Gel particles, photosensitive composition, ink composition, method of producing water dispersion of gel particles, and image forming method

ABSTRACT

Provided are gel particles each having a three-dimensional crosslinked structure including at least one bond selected from a urethane bond and a urea bond, the gel particles each including: a polymerizable group; and a functional group that generates radicals by irradiation with active energy rays, a photosensitive composition containing the gel particles, an ink composition, a method of producing water dispersion of gel particles, and an image forming method.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of InternationalApplication No. PCT/JP2015/074796, filed Aug. 31, 2015, the disclosureof which is incorporated herein by reference in its entirety. Further,this application claims priority from Japanese Patent Application No.2014-201982, filed Sep. 30, 2014, and Japanese Patent Application No.2015-061720, filed Mar. 24, 2015, the disclosures of which areincorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to gel particles, a photosensitivecomposition, an ink composition, a method of producing water dispersionof gel particles, and an image forming method.

2. Description of the Related Art

Examples of the image forming method that forms an image on a recordingmedium such as paper based on image data signals include anelectrophotographic method, a sublimation-type thermal transfer method,a fusion-type thermal transfer method, and an ink jet method. Forexample, the ink jet method can be performed with a cheap device, and animage is directly formed on a recording medium by ejecting ink only to arequired image portion. Therefore, the ink can be effectively used, andthus running cost is not expensive. The ink jet method makes lessnoises, and thus excellent as the image forming method.

Examples of the ink jet method include an image forming method obtainedby using ink for ink jet recording that can be cured by irradiation withactive energy rays. In this method, ink droplets are cured by beingirradiated with active energy rays immediately after ink ejection orafter a certain period of time, such that recording speed can beincreased and an image can be formed.

The ink that can be cured by irradiation with active energy raysgenerally contains a polymerizable compound and a polymerizationinitiator.

In the related art, various polymerization initiators that improvereactivity are suggested.

For example, JP2012-532238A discloses a polymerization initiatorobtained by bonding one or more bisacylphosphine oxide moieties to anoligomer or a polymer skeleton via a phosphorus atom. JP2006-28514Adiscloses a polymeric initiator including a dendritic polymer corehaving at least one functional group for initiation as a terminal.JP1994-80625A (JP-H06-80625A) discloses a triphenylsulfonium saltunit-based polymer compound.

SUMMARY OF THE INVENTION

In a case where polymerization initiators disclosed in JP2012-532238A,JP2006-28514A, and JP1994-80625A (JP-H06-80625A) are used as apolymerization initiator contained in the ink composition, reactivity ofthe polymerization initiator itself is satisfactory, but solubility towater is low. Therefore, the polymerization initiator and thepolymerizable compound independently exist in the ink composition, andthus there is a tendency that efficiency of the progress of thecrosslinking reaction is low, and film hardness of the cured film is notsufficient.

In a case of the cured film obtained by using ink in a compositionincluding the polymerizable compound and the polymerization initiator,low molecular weight components (components having a molecular weight of1,000 or less) such as unreacted polymerizable monomer, thepolymerization initiator, and residues of the polymerization initiatorremains in the cured film in some cases, and thus the low molecularweight components become one cause of various problems.

For example, a phenomenon in which the low molecular weight componentsremaining in the cured film move from the cured film to the outside,so-called migration occurs in some cases. If a migration amount of thelow molecular weight components in the cured film is great, odor of thecured film becomes strong, particularly in a case where the ink is usedfor printing on a package such as food packaging, a problem that theodor moves to inclusion or surrounding food may occur.

Meanwhile, the low molecular weight components remain in the cured film,and in a case where the low molecular weight components remain in thefilm, the low molecular weight components cause adverse influence on thefilm properties of the cured film.

Accordingly, an ink composition that suppresses migration of the lowmolecular weight components and does not deteriorate film properties isrequired.

In view of the circumstances as described above, an object of theembodiment of the invention is to provide gel particles in whichoccurrence of migration in which low molecular weight components movefrom the cured film to the outside of the film is suppressed such that afilm (for example, image) having excellent film hardness can beobtained, a photosensitive composition, an ink composition, a method ofproducing water dispersion of gel particles, and an image formingmethod.

Specific means for achieving the object includes the followings.

<1> Gel particles each having a three-dimensional crosslinked structureincluding at least one bond selected from a urethane bond and a ureabond, the gel particles each comprising: a polymerizable group; and afunctional group that generates radicals by irradiation with activeenergy rays.

<2> The gel particles according to <1>, in which the functional groupthat generates radicals by irradiation with active energy rays is agroup having at least one selected from an acetophenone structurerepresented by Formula A below, a monoacylphosphine oxide structurerepresented by Formula B below, and a bisacylphosphine oxide structurerepresented by Formula C below,

in Formulae A, B, and C, R's each independently represent a monovalentgroup or *-L-, at least one of R's in the respective formulae represents*-L-, L represents a divalent organic group, and * represents a bondingsite with a three-dimensional crosslinked structure.

<3> The gel particles according to <1> or <2>, each further comprising:a hydrophilic group on a surface.

<4> The gel particles according to any one of <1> to <3>, eachcomprising: a polymerizable monomer.

<5> A photosensitive composition comprising: the gel particles accordingto any one of <1> to <4>; and water.

<6> The photosensitive composition according to <5>, further comprising:a polymerizable compound outside the gel particles.

<7> An ink composition comprising: the gel particles according to anyone of <1> to <4>; water; and a colorant.

<8> The ink composition according to <7>, further comprising: apolymerizable compound outside the gel particles.

<9> A method of producing water dispersion of gel particles, comprising:an emulsification step of obtaining an emulsion, by mixing andemulsifying any one oil phase component selected from an oil phasecomponent including a trifunctional or higher isocyanate compound havinga functional group that generates radicals by irradiation with activeenergy rays, a polymerizable monomer, and an organic solvent, an oilphase component including a trifunctional or higher isocyanate compoundhaving a functional group that generates radicals by irradiation withactive energy rays, a trifunctional or higher isocyanate compound havinga polymerizable group, and an organic solvent, an oil phase componentincluding a trifunctional or higher isocyanate compound having apolymerizable group, a functional group that generates radicals byirradiation with active energy rays, a polymerizable monomer, and anorganic solvent, and an oil phase component including a trifunctional orhigher isocyanate compound having a functional group that generatesradicals by irradiation with active energy rays, a trifunctional orhigher isocyanate compound having a polymerizable group, a polymerizablemonomer, and an organic solvent, and a water phase component includingwater; and a gelation step of gelling the emulsion by heating.

<10> The method of producing water dispersion of gel particles accordingto <9>, further comprising: a mixture step of mixing the gel particlesobtained in the gelation step, water, and a colorant.

<11> An image forming method comprising: an ink applying step ofapplying the ink composition according to <7> or <8> on a recordingmedium; and an irradiation step of irradiating the ink compositionapplied on the recording medium with active energy rays.

According to an embodiment of the invention, occurrence of migration inwhich low molecular weight components move from a cured film to theoutside of the film is suppressed, gel particles for obtaining a film(for example, image) having excellent film hardness, a photosensitivecomposition, an ink composition, a method of producing water dispersionof gel particles, and an image forming method are provided.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, details of the gel particles are specifically described.

In this specification, a numerical range indicated by using theexpression “to” represents a range including numerical values indicatedbefore and after the expression “to” respectively as the minimum valueand the maximum value.

In this specification, (meth)acrylate means at least one of acrylate ormethacrylate.

In this specification, the expression “light” is a concept of includingactive energy rays such as γ rays, β rays, electron beams, ultravioletrays, visible rays, and infrared rays.

In this specification, the ultraviolet rays may be referred to as “ultraviolet (UV) light”.

In this specification, light generated from a light emitting diode (LED)light source may be referred to as “LED light”.

<Gel Particles>

The gel particles have a polymerizable group and a functional groupsthat generate radicals by irradiation with active energy rays and have athree-dimensional crosslinked structure including at least one bondselected from a urethane bond and a urea bond.

The use of the gel particles is not particularly limited, but gelparticles are, for example, an ink composition, a coating agent, anadhesive, and paint.

Details of working mechanisms in the embodiment of the invention are notclear but it is assumed as follows.

Since the gel particles have a polymerizable group and a functionalgroups that generate radicals by irradiation with active energy rays,when gel particles is irradiated with active energy rays, radicals aregenerated from the functional groups that generate radicals byirradiation with active energy rays. Accordingly, a polymerizable groupexisting in one gel particle and a polymerizable group existing in theother gel particle between gel particles adjacent to each other easilyreact with each other, so as to form a crosslinked structure between thegel particles. Therefore, the gel particles can form a cured filmwithout using a polymerization initiator, low molecular weightcomponents caused by unreacted substances of the polymerizationinitiator and residues of the polymerization initiator hardly remains inthe cured film. That is, it is considered that occurrence of migrationof the low molecular weight components in the cured film is suppressed,and physical properties of the formed film are not deteriorated.

If the gel particles have a three-dimensional crosslinked structure, thegel particles can form a film having excellent film hardness such assolvent resistance or the like.

Since the gel particles have functional groups that generate radicals byirradiation with active energy rays, a range of selection of thefunctional groups that generate radicals by irradiation with activeenergy rays to be introduced becomes wide, and thus a range of selectionof the light source to be used becomes wide. Accordingly, curingsensitivity can be improved compared with that in the related art.

For example, an acylphosphine oxide compound is a photopolymerizationinitiator having particularly excellent curing sensitivity with respectto the irradiation of the active energy rays.

However, the acylphosphine oxide compound have low solubility withrespect to water, and thus it is difficult to cause the acylphosphineoxide compound to be contained in an aqueous composition in the relatedart.

The gel particles have excellent sensitivity with respect to light asthe functional groups that generate radicals by irradiation with activeenergy rays in a three-dimensional structure of the gel particles, butit is possible to introduce a structure which is the same as theacylphosphine oxide compound or the like of which solubility to water islow, as a functional group, and thus it does not have to use aphotopolymerization initiator such as an acylphosphine oxide compound asan independent component.

In a case where the functional group that generates radicals byirradiation with active energy rays is a group having an acylphosphineoxide structure, sensitivity to light, particularly, sensitivity to LEDlight is improved.

The wavelength of the LED light is preferably 355 nm, 365 nm, 385 nm,395 nm, or 405 nm.

˜Polymerizable Group Having Gel Particles˜

In this specification, the expression “gel particles have polymerizablegroups” means that the gel particles have at least one of polymerizablegroups included in a three-dimensional crosslinked structure orpolymerizable groups that are not included in a three-dimensionalcrosslinked structure.

That is, in the gel particles, the polymerizable group may exist as apart of the three-dimensional crosslinked structure or may exist as aportion other than the three-dimensional crosslinked structure.

The expression “polymerizable groups exist as a portion other than thethree-dimensional crosslinked structure” indicate that monomers(hereinafter, also referred to as “polymerizable monomers”) havingpolymerizable groups are included in the gel particles, independentlyfrom the three-dimensional crosslinked structure.

In any case, the polymerizable group preferably exist in surfaceportions (portions coming into contact with water) of the gel particles.

The expression “gel particles have polymerizable groups” can be checkedby fourier transform infrared spectroscopic (FT-IR) analysis.

Details of the polymerizable groups included in the gel particles andthe monomer (polymerizable monomer) having polymerizable group aredescribed below.

˜Three-Dimensional Crosslinked Structure˜

The “three-dimensional crosslinked structure” refers to a threedimensional mesh structure formed by crosslinking. The gel particles areformed by forming a three-dimensional crosslinked structure in theparticles.

That is, in the specification, the expression “the particles have athree-dimensional crosslinked structure” has the same meaning as theexpression “the particles are the gel particles.

Whether gel particles having a three-dimensional crosslinked structureare included in a composition such as an ink composition is checked asfollows. The following operations are performed in the temperaturecondition of 25° C.

Samples are gathered from the ink composition. With respect to thegathered samples, 100 times by mass of tetrahydrofuran (THF) is addedand mixed with respect to the total solid content of the sample so as toprepare a diluent. With respect to the obtained diluent, centrifugationis performed under the conditions of 80,000 rpm and 40 minutes. Afterthe centrifugation, whether there are residues is visually checked. In acase where there are residues, the residues are re-dispersed with water,a redispersion liquid is prepared, and a particle size distribution ofthe redispersion liquid is measured in a light scattering method byusing a wet-type particle size distribution measuring device (LA-910,manufactured by Horiba Ltd.).

A case where particle size distribution can be checked by the operationdescribed above is determined that the ink composition includes gelparticles having a three-dimensional crosslinked structure.

The three-dimensional crosslinked structure can be formed by thereaction with a trifunctional or higher isocyanate compound or adifunctional isocyanate compound with a compound having two or moreactive hydrogen groups. Since at least one compound having three or morereactive groups (isocyanate group or active hydrogen group) are includedas a raw material used when gel particles are produced, the crosslinkingreaction three dimensionally progresses so as to form a threedimensional mesh structure.

The three-dimensional crosslinked structure in the gel particles ispreferably a product formed by the reaction between a trifunctional orhigher isocyanate compound and water.

The three-dimensional crosslinked structure in the gel particles ispreferably a product formed from the reaction between a trifunctional orhigher isocyanate compound having a functional group that generatesradicals by irradiation with active energy rays and water.

(Trifunctional or Higher Isocyanate Compound)

The trifunctional or higher isocyanate compound is a compound havingthree or more isocyanate groups in a molecule, and a compoundsynthesized in the methods below and well-known compounds can be used.Examples of the trifunctional or higher isocyanate compound, atrifunctional or higher aromatic isocyanate compound, a trifunctional orhigher aliphatic isocyanate compound.

Examples of the well-known compound include compounds disclosed in“Polurethane resin Handbook” (edited by Keiji Iwata, Nikkan KogyoShimbun, Ltd., (1987)).

The trifunctional or higher isocyanate compound is preferably a compoundhaving three or more isocyanate groups in a molecule represented byFormula 1 below.X

NCO)_(n)  Formula 1

In Formula 1, X represents an n-valent organic group.

In Formula 1, n is 3 or greater. n is preferably 3 to 10, morepreferably 3 to 8, and even more preferably 3 to 6.

The trifunctional or higher isocyanate compound is preferably a compoundderived from a difunctional isocyanate compound (compound having twoisocyanate groups in a molecule). The trifunctional or higher isocyanatecompound is more preferably an isocyanate compound derived from at leastone selected from isophorone diisocyanate, hexamethylene diisocyanate,trimethylhexamethylene diisocyanate,1,3-bis(isocyanatomethyl)cyclohexane, m-xylylene diisocyanate, anddicyclohexylmethane-4,4′-diisocyanate.

The expression “derived” means including a structure derived from a rawmaterial by using the compound in the raw material.

As the trifunctional or higher isocyanate compound, for example, acompound having three or more isocyanate groups in a molecule such as atrifunctional or higher isocyanate compound (adduct type), a trimer of adifunctional or higher isocyanate compound (biuret type or isocyanuratetype), and a formalin condensate of benzene isocyanate as an adductproduct (adduct) of a difunctional or higher isocyanate compound (acompound having two or more isocyanate groups in a molecule) and acompound having three or more active hydrogen groups in a molecule suchas trifunctional or higher polyol, polyamine, and polythiol ispreferable.

These trifunctional or higher isocyanate compounds may be a mixtureincluding a plurality of compounds, and a compound represented byFormula 2 or 3 provided below is preferably a main component of themixture and may include other components.

The “active hydrogen group” means at least one group selected from ahydroxyl group, a primary amino group, a secondary amino group, and amercapto group.

Adduct Type

An adduct type trifunctional or higher isocyanate compound is preferablya compound represented by Formula 2 or 3 below.

In Formulae 2 and 3, X represents a (l+m+n)-valent organic group, l, m,and n are respectively 0 or greater, and l+m+n is 3 or greater. l+m+n ispreferably 3 to 10, more preferably 3 to 8, and even more preferably 3to 6.

In Formulae 2 and 3, Y₁, Y₂, Y₃, Y₄, and Y₅ each independently representO, S, or NH, O or S is preferable, and O is more preferable.

In Formulae 2 and 3, Z represents a divalent organic group.

In Formulae 2 and 3, R₁, R₂, R₃, R₄, and R₅ each independently representa divalent organic group. It is preferable that the organic groupsrepresented by R₁, R₂, R₃, R₄, and R₅ each independently represent analkylene group that may have a substituent having 1 to 20 carbon atoms,a cycloalkylene group that may have a substituent having 1 to 20 carbonatoms, or an arylene group that may have a substituent having 1 to 20carbon atoms. It is more preferable that R₁, R₂, R₃, R₄, and R₅ eachindependently represent a group selected from groups represented by(3-1) to (3-11), (4-1) to (4-2), and (5-1) to (5-7) below. * representsa bonding site.

In Formulae 2 and 3, it is more preferable that R₁, R₂, R₃, R₄, and R₅each independently represent any one of a group (5-3) derived fromisophorone diisocyanate (IPDI), a group (5-7) derived from hexamethylenediisocyanate (HDI), groups (5-5 and 5-6) derived fromtrimethylhexamethylene diisocyanate (TMHDI), a group (5-4) derived from1,3-bis(isocyanatomethyl) cyclohexane, a group (5-1) derived fromm-xylylene diisocyanate (XDI), and a group (5-2) derived fromdicyclohexylmethane-4,4′-diisocyanate (*represents a bonding site).

An adduct type trifunctional or higher isocyanate compound can besynthesized by reacting a compound having three or more active hydrogengroups in a molecule described below and a difunctional or higherisocyanate compound described below. The active hydrogen group means ahydroxyl group, a primary amino group, a secondary amino group, and amercapto group.

For example, a compound having three or more active hydrogen groups in amolecule and a difunctional or higher isocyanate compound in an organicsolvent may be heated (50° C. to 100° C.) while stirring or may bestirred at a low temperature (0° C. to 70° C.) while adding a catalystsuch as a stannous octoate and an amine compound, so as to obtain theadduct type trifunctional or higher isocyanate compound (SynthesizationScheme 1 below).

Generally, as the number of moles (number of molecules) of thedifunctional or higher isocyanate compound to be reacted with thecompound having three or more active hydrogen groups in the molecule,0.6 times or greater of the number of moles (the number of molecules) ofthe difunctional or higher isocyanate compound with respect to thenumber of moles (equivalent number of active hydrogen group) of theactive hydrogen group in a compound having three or more active hydrogengroups in the molecule is used. The number of moles of the difunctionalor higher isocyanate compound is preferably 0.6 times to 5 times, morepreferably 0.6 times to 3 times, and even more preferably 0.8 times to 2times with respect to the number of moles of the active hydrogen group.

After an adduct (prepolymer) of a compound having two active hydrogengroups in a molecule and a difunctional or higher isocyanate compoundare synthesized, this prepolymer and a compound having three or moreactive hydrogen groups in a molecule are reacted with each other, so asto obtain the adduct type trifunctional or higher isocyanate compound(Synthesization Scheme 2 below).

Examples of the difunctional or higher isocyanate compound include adifunctional or higher aromatic isocyanate compound and a difunctionalor higher aliphatic isocyanate compound.

Specific examples of the difunctional or higher isocyanate compoundinclude isophorone diisocyanate (IPDI), m-phenylene diisocyanate,p-phenylene diisocyanate, 2,6-tolylene diisocyanate, 2,4-tolylenediisocyanate (TDI), naphthalene-1,4-diisocyanate,diphenylmethane-4,4′-diisocyanate (MDI), 3,3′-dimethoxy-biphenyldiisocyanate, 3,3′-dimethyl diphenylmethane-4,4′-diisocyanate,m-xylylene diisocyanate (XDI), p-xylylene diisocyanate,4-chloroxylene-1,3-diisocyanate, 2-methylxylylene-1,3-diisocyanate,4,4′-diphenylpropane diisocyanate, 4,4′-diphenylhexafluoropropanediisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate(HDI), propylene-1,2-diisocyanate, butylene-1,2-diisocyanate,cyclohexylene-1,2-diisocyanate, cyclohexylene-1,3-diisocyanate,cyclohexylene-1,4-diisocyanate, dicyclohexylmethane-4,4′-diisocyanate,1,4-bis(isocyanatomethyl) cyclohexane, 1,3-bis(isocyanatomethyl)cyclohexane (HXDI), norbornene diisocyanate (NBDI),trimethylhexamethylene diisocyanate (TMHDI), lysine diisocyanate, and1,3-bis(2-isocyanato-2-propyl) benzene.

Among these difunctional or higher isocyanate compounds, compoundshaving structures represented in (8-1) to (8-24) below are preferable.

Among these difunctional or higher isocyanate compounds, isophoronediisocyanate (IPDI), hexamethylene diisocyanate (HDI),trimethylhexamethylene diisocyanate (TMHDI), 1,3-bis(isocyanatomethyl)cyclohexane (HXDI), m-xylylene diisocyanate (XDI), andicyclohexylmethane-4,4′-diisocyanate are preferable.

As the difunctional or higher isocyanate compound, a difunctionalisocyanate compound derived from the compound can be also used. Examplesthereof include DURANATE (registered trademark) D101, D201, and A101(manufactured by Asahi Kasei Corporation).

The compound having three or more active hydrogen groups in a moleculeis a compound having three or more groups in at least one type of groupselected a hydroxyl group, a primary amino group, a secondary aminogroup, or a mercapto group in a molecule. Examples thereof include acompound of a structure represented (9-1) to (9-13) below. In thestructure below, n represents an integer selected from 1 to 100.

As the adduct-type trifunctional or higher isocyanate compounds,compounds obtained by reacting a compound having two or more activehydrogen groups in a molecule and difunctional or higher isocyanatecompounds are reacted with each other in combinations presented in Table1 below are preferably used.

TABLE 1 Composition Compound Polyisocyanate structure having two orDifunctional Compound having two more active isocyanate Compound or moreactive hydrogen hydrogen groups compound Number groups Difunctionalisocyanate compound (mol equivalent) (mol equivalent) NCO 101 NCO 102NCO 103 NCO 104   NCO 105

  Trimethylolpropane 2,4-tolylene diisocyanate (TDI) m-xylylenediisocyanate (XDI) Hexamethylene diisocyanate (HDI)1,3-bis(isocyanatomethyl) cyclohexane (HXDI) Isophorone diisocyanate(IPDI) 1 1 1 1   1 4 4 4 4   4 NCO 106 NCO 107

  1,3,5-trihydroxybenzene Hexamethylene diisocyanate (HDI) Isophoronediisocyanate (IPDI) 1 1 4 4 NCO 108   NCO 109

  Pentaerythritol ethylene oxide 1,3-bis(isocyanatomethyl) cyclohexane(HXDI) Isophorone diisocyanate (IPDI) 1   1 5   5 NCO 110 NCO 111

  Dipentaerythritol hexakis (3-mercaptopropionate) Hexamethylenediisocyanate (HDI) Isophorone diisocyanate (IPDI) 1 1 7 7 NCO 112 NCO113

  Triethanolamine Hexamethylene diisocyanate (HDI) Isophoronediisocyanate (IPDI) 1 1 4 4

The adduct-type trifunctional or higher isocyanate compound is morepreferably NCO102 to NCO105, NCO107, NCO108, NCO111, and NCO113 in thecompounds presented in Table 1 and even more preferably NCO103 toNCO105, and NCO109.

As the adduct-type trifunctional or higher isocyanate compound, productscommercially available in the market may be used, and examples thereofinclude D-101A, D-102, D-103, D-103H, D-103M2, P49-75S, D-110, D-120N,D-140N, and D-160N (manufactured by Mitsui Chemicals, Inc.), DESMODUR(registered trademark) L75 and UL57SP (manufactured by Covestro JapanLtd.), CORONATE (registered trademark) HL, HX, and L (manufactured byTOSOH Corporation), and P301-75E (manufactured by Asahi KaseiCorporation).

Among these adduct-type trifunctional or higher isocyanate compounds,D-110, D-120N, D-140N, and D-160N (manufactured by Mitsui Chemicals,Inc.) are more preferable.

Biuret Type or Isocyanurate Type

A biuret-type or isocyanurate-type trifunctional or higher isocyanatecompound is preferably a compound represented by Formula 4 or 5 below.

In Formulae 4 and 5, R₆, R₇, R₈, R₉, R₁₀, and R₁₁ each independentlyrepresent a divalent organic group. The organic groups represented byR₆, R₇, R₈, R₉, R₁₀, and R₁₁ each independently represent an alkylenegroup having 1 to 20 carbon atoms that may have a substituent, acycloalkylene group having 1 to 20 carbon atoms that may have asubstituent, and an arylene group having 1 to 20 carbon atoms that mayhave a substituent are preferable. It is preferable that R₆, R₇, R₈, R₉,R₁₀, and R₁₁ each independently represent a group selected from thegroups represented by (3-1) to (3-11), (4-1) to (4-2), and (5-1) to(5-7). * represents a bonding site.

It is more preferable that, in Formulae 4 and 5, R₆, R₇, R₈, R₉, R₁₀,and R₁₁ each independently represent a group (5-3) derived fromisophorone diisocyanate (IPDI), a group (5-7) derived from hexamethylenediisocyanate (HDI), a group (5-5) derived from trimethylhexamethylenediisocyanate (TMHDI), a group (5-4) derived from1,3-bis(isocyanatomethyl) cyclohexane, a group (5-1) derived fromm-xylylene diisocyanate (XDI), and a group (5-2) derived fromdicyclohexylmethane-4,4′-diisocyanate (*represents a bonding site).

As the biuret-type trifunctional or higher isocyanate compound, productscommercially available in the market may be used, and examples thereofinclude D-165N and NP1100 (manufactured by Mitsui Chemicals, Inc.),DESMODUR (registered trademark) N3200 (manufactured by Covestro JapanLtd.), and DURANATE (registered trademark) 24A-100 (manufactured byAsahi Kasei Corporation).

As the isocyanurate-type trifunctional or higher isocyanate compound,products commercially available in the market may be used, and examplesthereof include D-127, D-170N, D-17OHN, D-172N, and D-177N (manufacturedby Mitsui Chemicals, Inc.), SUMIDUR N3300, DESMODUR (registeredtrademark) N3600, N3900, and Z4470BA (manufactured by Covestro JapanLtd.), CORONATE (registered trademark) HX and HK (manufactured by TOSOHCorporation), and DURANATE (registered trademark) TPA-100, TKA-100,TSA-100, TSS-100, TLA-100, and TSE-100 (manufactured by Asahi KaseiCorporation).

Among these biuret-type and isocyanurate-type trifunctional or higherisocyanate compounds, DURANATE (registered trademark) 24A-100(manufactured by Asahi Kasei Corporation), D-127 (manufactured by MitsuiChemicals, Inc.), and TKA-100 and TSE-100 (manufactured by Asahi KaseiCorporation) are more preferable.

(Compound Having Water and Two or More Active Hydrogen Groups)

The gel particles are preferably produced by reacting the trifunctionalor higher isocyanate compound and a compound having water and two ormore active hydrogen groups.

As the compound obtained by reacting with a trifunctional or higherisocyanate compound, water is generally used. If the trifunctional orhigher isocyanate compound and water react with each other, athree-dimensional crosslinked structure having a urea bond is formed.

Examples of a compound to be caused to react with a trifunctional orhigher isocyanate compound other than water include a compound havingtwo or more active hydrogen groups, and as the compound having two ormore active hydrogen groups, polyfunctional alcohol, polyfunctionalphenol, polyfunctional amine a hydrogen atom on a nitrogen atom, andpolyfunctional thiol can also be used.

Specific examples of polyfunctional alcohol include propylene glycol,glycerin, trimethylolpropane, and 4,4′,4″-trihydroxytriphenylmethane.

Specific examples of polyfunctional amine include diethylenetriamine andtetraethylenepentamine.

Specific examples of polyfunctional thiol include 1,3-propanedithiol and1,2-ethanedithiol.

Specific examples of polyfunctional phenol include bisphenol A.

These compounds may be used singly or two or more types thereof may beused in combination.

The compound having three or more active hydrogen groups in a moleculeis also included in the compound having two or more active hydrogengroups.

(Functional groups that generate radicals by irradiation with activeenergy rays)

The gel particles have functional groups that generate radicals byirradiation with active energy rays.

The functional groups that generate radicals by irradiation with activeenergy rays may exist on the surfaces of the gel particles or may existinside the gel particles. The functional groups that generate radicalsby irradiation with active energy rays are preferably bonded tothree-dimensional crosslinked structures of the gel particles viacovalent bonds. The functional groups that generate radicals byirradiation with active energy rays may be bonded to three-dimensionalcrosslinked structures via one covalent bond or may be bonded tothree-dimensional crosslinked structures via two or more covalent bonds.

With respect to the functional group that generates radicals byirradiation with active energy rays, an aspect in which all of theplurality of generated radical species are bonded to the gel particlesvia the covalent bonds is referred to as a “main chain-type” functionalgroup, and an aspect in which a portion of the plurality of generatedradical species is bonded to the gel particles via the covalent bonds isreferred to as a “side chain-type” functional group.

If the functional groups that generate radicals by irradiation withactive energy rays exist in the gel particles, radicals (initiatingspecies) are generated by the irradiation of the active energy rays. Ifthese initiating species propagate to the polymerizable group, thepolymerizable groups are bonded to the polymerizable group existing inthe adjacent gel particles, so as to form a crosslinked structure.

If the the functional groups that generate radicals by irradiation withactive energy rays and the polymerizable groups exist in the gelparticles, the initiating species easily propagate, and thus it ispossible to form a film having excellent film hardness with highsensitivity.

The functional group that generates radicals by irradiation with activeenergy rays is preferably a group having at least a structure selectedfrom an acetophenone structure represented by Formula A below, amonoacylphosphine oxide structure represented by Formula B below, and abisacylphosphine oxide structure represented by Formula C below.

In Formulae A, B, and C, R's each independently represent a monovalentgroup or *-L-, and at least one of R's in the respective formulas is*-L-. L represents a divalent organic group, * represents a bonding siteto a three-dimensional crosslinked structure.

Examples of the monovalent group represented by R include an organicgroup such as an aliphatic group and an aromatic group, —H, —OH, —SH,—NH, —NH₂, or -L-R₁, and —H, —OH, —SH, —NH, —NH₂, or -L-R₁ ispreferable. R₁ represents a monovalent organic group and is preferably—H, —OH, —SH, —NH, or —NH₂.

The divalent organic group represented by L is preferably a divalentaliphatic group, a divalent aromatic group, a divalent heterocyclic ringgroup, —O—, —S—, —NH—, —CO—, —SO—, —SO₂—, or a combination thereof.

The functional group that generates radicals by irradiation with activeenergy rays is more preferably a group having at least one structureselected from an α-aminoalkylphenone structure represented by Formula Dbelow, an α-hydroxyalkylphenone structure represented by Formula Ebelow, a monoacylphosphine oxide structure represented by Formula Fbelow, and a bisacylphosphine oxide structure represented by Formula Gbelow.

In Formulae D, E, F, and G, R's each independently represent amonovalent group or *-L-, and at least one of R's in the respectiveformulas is *-L-. L represents a divalent organic group, * represents abonding site to a three-dimensional crosslinked structure. A preferableaspect of R is the same as R in Formulae A, B, and C.

The functional group that generates radicals by irradiation with activeenergy rays is even more preferably a group having at least onestructure selected from an α-aminoalkylphenone structure represented byFormula H below, an α-hydroxyalkylphenone structure represented byFormula I below, a monoacylphosphine oxide structure represented byFormula J below, a bisacylphosphine oxide structure represented byFormula K below, and a bisacylphosphine oxide structure represented byFormula L below. In view of suitability to LED light, the functionalgroup that generates radicals by irradiation with active energy rays isparticularly preferably a group having at least one structure selectedfrom a monoacylphosphine oxide structure represented by Formula J below,a bisacylphosphine oxide structure represented by Formula K below, and abisacylphosphine oxide structure represented by Formula L below.

In Formulae H, I, J, K, and L, R's each independently represent amonovalent group, L represents a divalent organic group, * represents abonding site to a three-dimensional crosslinked structure. Preferableaspects of R and L are the same as R and L in Formulae A, B, and C.

In a case where the functional groups that generate radicals byirradiation with active energy rays are introduced to the gel particles,a compound having a functional group that generates radicals byirradiation with active energy rays can be used. This compound may haveat least one functional group that generates radicals by irradiationwith active energy rays. Among these, a compound having at least oneactive hydrogen group and at least one functional group that generatesradicals by irradiation with active energy rays is preferable.

Hereinafter, compounds (Exemplary Compound INT-1 to INT-15) each havingat least one active hydrogen group and at least one functional groupthat generates radicals by irradiation with active energy rays areprovided. However, an embodiment of the invention is not limited to thisstructures.

Introduction of the functional groups that generate radicals byirradiation with active energy rays to the gel particles can beperformed, for example, reacting an isocyanate group of a difunctionalor higher isocyanate compound represented by Synthesization Scheme 3below and an active hydrogen atom of a compound having at least oneactive hydrogen group and at least one functional group that generatesradicals by irradiation with active energy rays, produced an isocyanatecompound to which a functional group that generates radicals byirradiation with active energy rays is introduced, and reacting theproduced isocyanate compound to which the functional group thatgenerates radicals by irradiation with active energy rays is introducedwith water or the compound having two or more active hydrogen groups.

In a case where the isocyanate compound to which the functional groupthat generates radicals by irradiation with active energy rays isintroduced when the gel particles are produced, a compound obtained byreacting a compound (initiator in Table 2) having at least one activehydrogen group and at least one functional group that generates radicalsby irradiation with active energy rays in the combination represented inTable 2 below, with a difunctional or higher isocyanate compound(isocyanate compound in Table 2) is preferably used.

TABLE 2 Composition Addition method Amount of active hydrogen Bindingmethod to Compound groups of initiator with respect three-dimensionalCompound Isocyanate to NCO group of isocyanate crosslinked NumberInitiator compound compound (mol %) structure INT-NCO 1 INT-1 NCO 103 40Side chain type INT-NCO 2 INT-2 NCO 105 40 Main chain type INT-NCO 3INT-3 NCO 109 30 Main chain type INT-NCO 4 INT-4 TDI 37.5 Main chaintype INT-NCO 5 INT-4 HXDI 37.5 Main chain type INT-NCO 6 INT-4 HDI 37.5Main chain type INT-NCO 7 INT-4 IPDI 37.5 Main chain type INT-NCO 8INT-4 XDI 37.5 Main chain type INT-NCO 9 INT-5 NCO 103 40 Main chaintype INT-NCO 10 INT-5 NCO 104 40 Main chain type INT-NCO 11 INT-5 NCO109 30 Main chain type INT-NCO 12 INT-5 DURANATE 24A-100 40 Main chaintype INT-NCO 13 INT-5 TSE-100 40 Main chain type INT-NCO 14 INT-6 NCO110 20 Main chain type INT-NCO 15 INT-7 DURANATE TKA-100 40 Main chaintype INT-NCO 16 INT-8 NCO 103 40 Main chain type INT-NCO 17 INT-8 NCO109 30 Main chain type INT-NCO 18 INT-8 TSE-100 40 Main chain typeINT-NCO 19 INT-9 NCO 103 40 Side chain type INT-NCO 20 INT-10 IPDI 37.5Side chain type INT-NCO 21 INT-11 HDI 40 Side chain type INT-NCO 22INT-11 HXDI 40 Side chain type INT-NCO 23 INT-11 TMHDI 40 Side chaintype INT-NCO 24 INT-12 DURANATE TKA-100 40 Side chain type INT-NCO 25INT-13 IPDI 37.5 Main chain type INT-NCO 26 INT-14 NCO-112 40 Main chaintype INT-NCO 27 INT-15 HXDI 37.5 Main chain type

A compound having at least one active hydrogen group and at least onefunctional group that generates radicals by irradiation with activeenergy rays may be used singly or two or more types thereof may be usedin combination.

With respect to the active hydrogen group of the compound (in Table 2,indicated as an initiator) having at least one active hydrogen group andat least one functional group that generates radicals by irradiationwith active energy rays and the isocyanate group of the difunctional orhigher isocyanate compound (in Table 2, indicated as an isocyanatecompound), the number of moles of the active hydrogen group in thecompound having at least one active hydrogen group and at least onefunctional group that generates radicals by irradiation with activeenergy rays is preferably reacted in an amount of the number of moles ofthe isocyanate group of the difunctional or higher isocyanate compoundof 0.01 times to 0.6 times (1 mol % to 60 mol %), is more preferablyreacted in an amount of 0.05 times to 0.5 times (5 mol % to 50 mol %),and is even more preferably reacted in an amount of 0.1 times to 0.4times (10 mol % to 40 mol %).

(Polymerizable Group of Gel Particles)

The Gel Particles Have Polymerizable Groups.

The gel particles may further have a polymerizable group. The gelparticles may have the polymerizable group by introducing thepolymerizable group to the three-dimensional crosslinked structure ormay have the polymerizable group by including the polymerizable monomerinside the gel particles (voids of three-dimensional crosslinkedstructure). Both may coexist.

The gel particles preferably have polymerizable groups on the surfacesof the gel particles, in view of sensitivity and crosslinkingproperties.

If the gel particles have polymerizable groups, the gel particlesadjacent to each other are bonded to each other by the irradiation ofthe active energy rays so as to form a crosslinked structure, and a filmhaving high crosslinking properties and excellent film hardness can beformed.

Examples of the method of introducing the polymerizable groups to thegel particles include a method of reacting a compound having thetrifunctional or higher isocyanate compound and water or the two or moreactive hydrogen groups, and the polymerizable compound as apolymerizable group-introduced monomer, when a three-dimensionalcrosslinked structure having at least one bond selected from a urethanebond and a urea bond is formed, a method of reacting the difunctional orhigher isocyanate compound and the polymerizable compound as thepolymerizable group-introduced monomer when the trifunctional or higherisocyanate compound is produced and reacting an isocyanate compound towhich a polymerizable group is introduced in advance and a compoundhaving water or the two or more active hydrogen groups, and a method ofdissolving a polymerizable compound as a polymerizable group-introducedmonomer together with a component for forming gel particles when the gelparticles are produced in an oil phase component, adding a water phasecomponent to an oil phase component, performing mixture, and performingemulsification.

Examples of the polymerizable compound used in the introduction of thepolymerizable group to the gel particles include a compound having atleast one active hydrogen group and an ethylenically unsaturated bond atat least one terminal.

The compound having at least one active hydrogen group and anethylenically unsaturated bond at at least one terminal can berepresented by Structural Formula (a) below.L¹Lc_(m)Z_(n)  (a)

In Structural Formula (a), L¹ represents a m+n-valent linking group, mand n each independently represent an integer selected from 1 to 100, Lcrepresents a monovalent ethylenically unsaturated group, Z represents anactive hydrogen group.

L¹ preferably divalent or higher aliphatic group, preferably divalent orhigher aromatic group, preferably divalent or higher heterocyclic ringgroup, —O—, —S—, —NH—, —N<, —CO—, —SO—, —SO₂—, or a combination thereof.m and n each independently and preferably represent 1 to 50, morepreferably 2 to 20, even more preferably 3 to 10, and particularlypreferably 3 to 5.

Examples of the monovalent ethylenically unsaturated group representedby Lc include an allyl group, a vinyl group, an acryloyl group, amethacryloyl group, and an acrylamide group.

Z is preferably OH, SH, NH, or NH₂, more preferably OH or NH₂, and evenmore preferably OH.

Examples of the compound having at least one active hydrogen group andthe ethylenically unsaturated bond at at least one terminal are providedbelow, but the invention is not limited to these structures. n inCompounds (11-3) and (12-2) represents, for example, an integer selectedfrom 1 to 90.

As the compound having at least one active hydrogen group and anethylenically unsaturated bond at at least one terminal, productscommercially available in the market may be used. Examples thereofinclude acrylates such as hydroxyethyl acrylate (manufactured by OsakaOrganic Chemical Industry Ltd.), 4-hydroxybutyl acrylate,1,4-cyclohexanedimethanol monoacrylate (manufactured by Nippon KaseiChemical Co., Ltd.), BLEMMER (registered trademark) AE-90U (n=2), AE-200(n=4.5), AE-400 (n=10), AP-150 (n=3), AP-400 (n=6), AP-550 (n=9), andAP-800 (n=13) (manufactured by NOF Corporation), and DENACOL (registeredtrademark) ACRYLATE DA-212, DA-250, DA-314, DA-721, DA-722, DA-911M,DA-920, and DA-931 (manufactured by Nagase ChemteX Corporation),methacrylate such as 2-hydroxyethyl methacrylate (manufactured byKyoeisha Chemical Co., Ltd.), BLEMMER (registered trademark) PE-90(n=2), PE-200 (n=4.5), PE-350 (n=8), PP-1000 (N=4 to 6), PP-500 (n=9),and PP-800 (n=13) (manufactured by NOF Corporation), and acrylamide(manufactured by KJ Chemicals Corporation).

Among the compounds having at least one active hydrogen group and theethylenically unsaturated bond at at least one terminal, hydroxyethylacrylate (manufactured by Osaka Organic Chemical Industry Ltd.), AE-400(n=10), AP-400 (n=6) (manufactured by NOF Corporation), DENACOL(registered trademark) ACRYLATE DA-212 (manufactured by Nagase ChemteXCorporation), and PP-500 (n=9) (manufactured by NOF Corporation) arepreferable.

The introduction of the polymerizable group to the gel particles can beperformed by reacting an isocyanate group of a trifunctional or higherisocyanate compound as represented by Synthesization Scheme 4 below andan active hydrogen group of a compound having at least one activehydrogen group and an ethylenically unsaturated bond at at least oneterminal so as to produce the isocyanate compound to which thepolymerizable group is introduced and reacting the produced isocyanatecompound to which the polymerizable group is introduced and the compoundhaving two or more active hydrogen groups with each other.

(Hydrophilic Group on Surface of Gel Particles)

The gel particles preferably further has hydrophilic groups on surfacesthereof.

If the gel particles have hydrophilic groups on the surface thereof,dispersibility in the aqueous medium is further improved. Therefore, ina case where gel particles are applied to the ink composition or thephotosensitive composition, dispersibility of the gel particles in theink composition or the like can be further improved.

In the gel particles, the hydrophilic groups may exist as portions ofthe three-dimensional crosslinked structure and may exist as portionsexcept for the three-dimensional crosslinked structure.

Here, the expression “hydrophilic groups exist as portions of thethree-dimensional crosslinked structure” means that the hydrophilicgroups form covalent bonds with portions other than the hydrophilicgroups of the three-dimensional crosslinked structure.

The expression “hydrophilic groups exist as portions other than thethree-dimensional crosslinked structure” means that gel particlesinclude an organic compound having a hydrophilic group independentlyfrom the three-dimensional crosslinked structure.

Examples of the hydrophilic group existing on the surface portions ofthe gel particles include a carboxylic acid group, a salt of acarboxylic acid group, a phosphonic acid group, a salt of a phosphonicacid group, a phosphoric acid group, a salt of a phosphoric acid group,a sulfonic acid group, a salt of a sulfonic acid group, a sulfuric acidgroup, a salt of a sulfuric acid group, a group having a polyetherstructure and a group having a betaine structure. In this specification,the “hydrophilic group” is different from the active hydrogen group (ahydroxyl group, a primary amino group, a secondary amino group, and amercapto group).

A salt of a carboxylic acid group, a salt of a sulfonic acid group, asalt of a sulfuric acid group, a salt of a phosphonic acid group, and asalt of a phosphoric acid group may be salts formed in the course ofproduction or neutralization of the gel particles. In a case where thegel particles have hydrophilic groups on the surface thereof, the gelparticles may have only one type of hydrophilic group or may have two ormore types thereof.

The hydrophilic groups that are introduced to the surfaces of the gelparticles are preferably at least one type selected from a group havinga polyether structure, a carboxylic acid group, and a salt of acarboxylic acid group.

The introduction of the hydrophilic group to the surfaces of the gelparticles can be performed by reacting the trifunctional or higherisocyanate compound and the compound having two or more active hydrogengroup with the compound having the hydrophilic group. The introductionmay be performed by causing the difunctional or higher isocyanatecompound and the compound having the hydrophilic group area to reactwith each other when the trifunctional or higher isocyanate compound isproduced and causing the isocyanate compound to which the hydrophilicgroup is introduced in advance and the compound having the two or moreactive hydrogen group to react with each other.

Examples of the compound having a hydrophilic group used in theintroduction of the hydrophilic group to the surfaces of the gelparticles include a compound having the hydrophilic group.

As the compound having the hydrophilic group, a compound having a grouphaving a polyether structure, a compound having a carboxylic acid groupand a compound having a salt of a carboxylic acid group are preferable.

Examples of the compound having a group having a polyether structureinclude a compound having a polyoxyalkylene chain. Specific examplesthereof include polyethylene oxide, polypropylene oxide,polytetramethylene oxide, polystyrene oxide, polycyclohexylene oxide, apolyethylene oxide-polypropylene oxide block copolymer, and apolyethylene oxide-polypropylene oxide random copolymer.

Among these compounds having polyoxyalkylene chains, polyethylene oxide,polypropylene oxide, and a polyethylene oxide-polypropylene oxide blockcopolymer, are preferable, and polyethylene oxide is more preferable.

As the compound having a group having a polyether structure, monoetherof polyethylene oxide (examples of monoether include monomethyl etherand monoethyl ether), monoester of polyethylene oxide (examples ofmonoester include monoacetic acid ester, and mono(meth)acrylic acidester) are also preferable.

Specific examples of the compound having a carboxylic acid group or anionic hydrophilic group include the followings. The compound having acarboxylic acid group or other ionic hydrophilic groups may be used bypartially neutralizing an inorganic salt group such as sodium hydroxideand an organic acid group such as triethylamine.

In a case where an isocyanate compound to which a hydrophilic group isintroduced is used for introducing a hydrophilic group to surfaces ofthe gel particles, a reactant of a compound having a hydrophilic groupwith isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI),trimethylhexamethylene diisocyanate (TMHDI), 1,3-bis(isocyanatomethyl)cyclohexane (HXDI), m-xylylene diisocyanate (XDI), ordicyclohexylmethane-4,4′-diisocyanate (HMDI) is preferably used.

In a case where a group having a polyether structure is introduced tothe surfaces of the gel particles as a hydrophilic group, an adduct oftrimethylolpropane (TMP), m-xylylene diisocyanate (XDI), andpolyethylene glycol monomethyl ether (EO) (for example, TAKENATE(registered trademark) D-116N manufactured by Mitsui Chemicals, Inc.) ispreferably used.

In a case where carboxylic acid groups or a salt of carboxylic acidgroups are introduced to the surfaces of the gel particles, as thehydrophilic groups, it is preferable to use a reactant (an isocyanatecompound including a carboxylic acid group or a salt of a carboxylicacid group) of 2,2-bis(hydroxymethyl) propionic acid (DMPA) or a salt of2,2-bis(hydroxymethyl) propionic acid (DMPA) with isophoronediisocyanate (IPDI). As the salt of the carboxylic acid group, a sodiumsalt, a potassium salt, a triethylamine salt, and a dimethylethanolaminesalt are preferable, and a sodium salt and a triethylamine salt are morepreferable.

The added amount of the compound having the hydrophilic group used inthe introduction of the hydrophilic group to the surfaces of the gelparticles is preferably 0.1 mass % to 50 mass %, more preferably 0.1mass % to 45 mass %, even more preferably 0.1 mass to 40 mass %, evenmore preferably 1 mass % to 35 mass %, and even more preferably 3 mass %to 30 mass % with respect to the mass of the gel particles.

(Polymerizable Monomer)

It is preferable that the gel particles further include thepolymerizable monomer.

An aspect in which the gel particles include the polymerizable monomersis advantageous in view of improving curing sensitivity of the film andhardness of the film.

In a case where the gel particles include the polymerizable monomers,the polymerizable groups of the polymerizable monomers function aspolymerizable groups included in the gel particles.

The polymerizable monomers (hereinafter, referred to as includedpolymerizable monomers) included in the gel particles can be selectedfrom the polymerizable monomers having the radically polymerizableethylenically unsaturated bonds.

Inclusion

In this specification, for example, the expression “polymerizablemonomers are included inside the gel particles” means that thepolymerizable monomers are included in the gel particles. The expression“inside the gel particles” means voids of the three-dimensionalcrosslinked structure.

An inclusion ratio (mass %) of the polymerizable monomers in the gelparticles is preferably 50 mass % or greater, more preferably 70 mass %or greater, and more preferably 80 mass % or greater.

In a case where two or more types of polymerizable monomers are includedin the water dispersion, it is preferable that the inclusion ratio of atleast one polymerizable monomer is in the range described above.

Here, the inclusion ratio (mass %) of the polymerizable monomer means anamount of the polymerizable monomers included in the gel particles withrespect to the total amount of the polymerizable monomers in the waterdispersion in a case where the water dispersion of the gel particles areprepared and refers to a value obtained as follows. The method ofproducing the water dispersion of the gel particles is described below.

—Method of Measuring Inclusion Ratio (mass %) of Polymerizable Monomer—

The following operations are performed in the liquid temperaturecondition of 25° C.

The following operations are performed by using this water dispersionwithout change in a case where the water dispersion does not contain apigment. In a case where the water dispersion contains a pigment, apigment is first removed from the water dispersion by centrifugation,and the following operations are performed on the water dispersion fromwhich the pigment is removed.

First, the water dispersion of the gel particles which is a measurementtarget of the inclusion ratio (mass %) of the polymerizable monomer isprepared, two samples (hereinafter, referred to as “Sample 1” and“Sample 2”) in the same masses are gathered from the prepared waterdispersion.

100 times by mass of tetrahydrofuran (THF) with respect to the totalsolid content of Sample 1 is added and mixed to Sample 1, so as toprepare the diluent. Centrifugation is performed on the obtaineddiluent, under conditions of 80,000 rpm (round per minute; the same isapplied hereinafter) and 40 minutes. A supernatant (hereinafter,referred to as “Supernatant 1”) generated by the centrifugation isgathered. In this operation, it is considered that all polymerizablemonomers included in Sample 1 are extracted into Supernatant 1. The massof the gathered polymerizable monomers included in Supernatant 1 ismeasured by liquid chromatography (for example, a liquid chromatographydevice manufactured by Waters Corporation). The obtained mass of thepolymerizable monomers is set as “a total amount of the polymerizablemonomer”.

Centrifugation is performed on Sample 2 under the same conditions of thecentrifugation performed on the diluent. The supernatant (hereinafter,referred to as “Supernatant 2”) generated by the centrifugation isgathered. In this operation, polymerizable monomers which are notincluded in (that is, which are liberated from) the gel particles inSample 2 are extracted to Supernatant 2. The mass of the gatheredpolymerizable monomers included in Supernatant 2 is measured by liquidchromatography (for example, a liquid chromatography device manufacturedby Waters Corporation). The mass of the obtained polymerizable monomersis set as a “liberation amount of the polymerizable monomer”.

The inclusion ratio (mass %) of the polymerizable monomer is obtainedbased on the “total amount of the polymerizable monomer” and the“liberation amount of the polymerizable monomer” by the equation below.Inclusion ratio (mass %) of polymerizable monomers=((the total amount ofpolymerizable monomer−liberation amount of polymerizable monomer)/thetotal amount of polymerizable monomer)×100

Examples of the polymerizable monomer having a radically polymerizableethylenically unsaturated bond used as the included polymerizablemonomer include a monomer having an ethylenically unsaturated group,acrylonitrile, styrene, and various radically polymerizable monomerssuch as unsaturated polyester, unsaturated polyether, unsaturatedpolyamide, and unsaturated urethane.

The included polymerizable monomer is preferably a monomer having anethylenically unsaturated group.

The included polymerizable monomer may be used singly or two or moretypes thereof may be used in combination.

The included polymerizable monomer is preferably at least one of a(meth)acrylate monomer or a vinyl ether monomer and more preferably a(meth)acrylate monomer.

Specific examples of the included polymerizable monomer include acrylatemonomers such as 2-hydroxyethyl acrylate, butoxyethyl acrylate, carbitolacrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate, benzylacrylate, tridecyl acrylate, 2-phenoxyethyl acrylate,bis(4-acryloxypolyethoxyphenyl) propane, polyethylene glycol diacrylate,polypropylene glycol diacrylate, dipentaerythritol tetraacrylate,trimethylolpropane triacrylate (for example, A-TMPT manufactured by ShinNakamura Chemical Co., Ltd.), pentaerythritol triacrylate (for example,A-TMM-3L manufactured by Shin Nakamura Chemical Co., Ltd.),ditrimethylolpropane tetraacrylate (for example, AD-TMP manufactured byShin Nakamura Chemical Co., Ltd.), dipentaerythritol pentaacrylate (forexample, SR-399E manufactured by Sartomer), dipentaerythritolhexaacrylate (for example, A-DPH manufactured by Shin Nakamura ChemicalCo., Ltd.), oligoester acrylate, N-methylol acrylamide, diacetoneacrylamide, epoxy acrylate, isobornyl acrylate, dicyclopentenylacrylate, dicyclopentenyloxyethyl acrylate, dicyclopentanyl acrylate,neopentyl glycol propylene oxide adduct diacrylate (NPGPODA) (forexample, SR9003 manufactured by Sartomer); methacrylate monomers such asmethyl methacrylate, n-butyl methacrylate, allyl methacrylate, glycidylmethacrylate, benzyl methacrylate, dimethylaminomethyl methacrylate,polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate,and 2,2-bis(4-methacryloxypolyethoxyphenyl) propane; and vinyl ethermonomers such as allyl glycidyl ether, diallyl phthalate, triallyltrimellitate, cyclohexanedimethanol vinyl ether (for example, SHDVEmanufactured by Shin Nakamura Chemical Co., Ltd.), and trimethylpropanetrivinyl ether (for example, TMPTVE manufactured by Shin NakamuraChemical Co., Ltd.).

Among these included polymerizable monomers, trimethylolpropanetriacrylate, pentaerythritol triacrylate, ditrimethylolpropanetetraacrylate, dipentaerythritol pentaacrylate, cyclohexane dimethanolvinyl ether, trimethylpropane trivinyl ether (TMPTVE), dipentaerythritolhexaacrylate, or neopentyl glycol propylene oxide adduct diacrylate arepreferable, and dipentaerythritol pentaacrylate, cyclohexane dimethanolvinyl ether, or trimethylpropane trivinyl ether are more preferable.

In view of crosslinking properties and film hardness, the includedpolymerizable monomer is preferably a polyfunctional polymerizablemonomer, more preferably a trifunctional or higher polymerizablemonomer, and even more preferably a tetrafunctional or higherpolymerizable monomer.

In addition to the included polymerizable monomers described above,commercially available products or radical polymerizable andcrosslinkable monomers well-known in the art disclosed in “CrosslinkingAgent Handbook” edited by Shinzo Yamashita (Taiseisha, 1981); “UV/EBCuring Handbook (Raw Materials)” edited by Kiyomi Kato (KobunshiKankoukai, 1985); “Application and Market of UV/EB Curing Technology”,p. 79, edited by RadTech (CMC, 1989); and “Polyester Resin Handbook”(The Nikkan Kogyo Shimbun Ltd., 1988) edited by Eiichiro Takiyama can beused.

As the included polymerizable monomers, for example, photocurablepolymerizable monomers used in photopolymerizable compositions which aredisclosed in JP1995-159983A (JP-H07-159983A), JP1995-31399A(JP-H07-31399A), JP1996-224982A (JP-H08-224982A), JP1998-863A(JP-H10-863A), JP1997-134011A (JP-H09-134011A), and JP2004-514014A areknown, and these can be also applied to the gel particles.

As the included polymerizable monomers, products commercially availablein the market may be used, and examples thereof include ethoxylated orpropoxylated acrylate such as AH-600, AT-600, UA-306H, UA-306T, UA-3061,UA-510H, UF-8001G, and DAUA-167 (manufactured by Kyoeisha Chemical Co.,Ltd.), SR444, SR454, SR492, SR499, CD501, SR502, SR9020, CD9021, SR9035,and SR494 (manufactured by Sartomer), and isocyanur monomers such asA-9300 and A-9300-1CL (manufactured by Shin Nakamura Chemical Co.,Ltd.).

In addition, as the polymerizable monomer, commercially availableproducts such as NPGPODA (neopentyl glycol propylene oxide adductdiacrylate, Sartomer), SR399E (dipentaerythritol pentaacrylate,Sartomer), ATMM-3L (pentaerythritol triacrylate, Shin Nakamura ChemicalCo., Ltd.), and A-DHP (dipentaerythritol hexaacrylate, Shin NakamuraChemical Co., Ltd.) can be suitably used.

When the gel particles are produced, the included polymerizable monomersare dissolved as a oil phase component together with components thatform the gel particles, the water phase component is added to the oilphase component and mixing and emulsifying are performed, such that theincluded polymerizable monomers are included in the gel particles.

As the weight-average molecular weight, the molecular weight of theincluded polymerizable monomer is preferably 100 to 100,000, morepreferably 100 to 30,000, even more preferably 100 to 10,000, even morepreferably 100 to 1,000, even more preferably 100 to 900, even morepreferably 100 to 800, and particularly preferably 150 to 750. The lowerlimit of the weight-average molecular weight of the includedpolymerizable monomer may be 200 or may be 250.

The weight-average molecular weight can be measured by gel permeationchromatography (GPC). The measuring method is as described below.

In the gel particles, the content of the included polymerizable monomeris preferably 0.1 mass % to 75 mass %, more preferably 0.5 mass % to 60mass %, and even more preferably 1 mass % to 50 mass % with respect tothe total solid content of the gel particles. If the content is in therange described above, it is possible to obtain a film havingsatisfactory crosslinking properties and satisfactory film hardness.

˜Physical Properties of Gel Particles˜

In view of dispersibility, the volume-average particle diameter of thegel particles is preferably 0.01 μm to 10.0 μm, more preferably 0.01 μmto 5 μm, and even more preferably 0.05 μm to 1 μm.

The volume-average particle diameter of the gel particles can bemeasured by a light scattering method. As the volume-average particlediameter in this specification, a value measured by a wet-type particlesize distribution measuring device LA-910 (manufactured by Horiba Ltd.)is used.

Whether components other than the polymerizable monomers are included inthe gel particles can be checked in the same method as the method ofexamining whether the polymerizable monomers are included.

However, with respect to the compound having a molecular weight of 1,000or greater, the masses of the compounds included in Supernatants 1 and 2are measured by gel permeation chromatography (GPC) and are respectivelyset as a “total amount of the compound” and a “liberation amount of thecompound, so as to obtain an inclusion ratio (mass %) of the compound.

In the measurement by the gel permeation chromatography (GPC), HLC(registered trademark)-8020GPC (Tosoh Corporation) can be used as ameasuring device, three items of TSK gel (registered trademark) SuperMultipore HZ-H (4.6 mm ID×15 cm, Tosoh Corporation) can be used ascolumns, and tetrahydrofuran (THF) can be used as an eluent. As themeasurement condition, the sample concentration is set as 0.45 mass %,the flow rate is set as 0.35 ml/min, the sample injection volume is setas 10 μl, the measurement temperature is set as 40° C., and adifferential refractive index (RI) detector can be used.

The calibration curve can be produced from eight samples of “standardsample TSK standard, polystyrene” of Tosoh Corporation: “F-40”, “F-20”,“F-4”, “F-1”, “A-5000”, “A-2500”, “A-1000”, and “n-propylbenzene”.

<Ink Composition>

The ink composition has the polymerizable group and the functionalgroups that generate radicals by irradiation with active energy rays andcontains gel particles having a three-dimensional crosslinked structurehaving at least one bond selected from a urethane bond and a urea bond,water, and a colorant.

In order to contain gel particles according to the embodiment of theinvention, the ink composition suppresses occurrence of the migration ofthe low molecular weight components such that a film having excellentfilm hardness (for example, an image) can be obtained.

The ink composition can be suitably used in the ink jet recording.

In view of the dispersibility and crosslinking properties, the gelparticles are preferably contained by 1 mass % to 50 mass %, are morepreferably contained by 3 mass % to 40 mass %, are even more preferablycontained by 5 mass % to 35 mass % in a solid content of the gelparticles with respect to the total mass of the ink composition.

In a case where compounds such as the polymerizable monomers areincluded inside the particles (voids of three-dimensional crosslinkedstructure), the content of the gel particles is a value also includingmasses of these compounds.

The total solid content of the gel particles is preferably 50 mass % orgreater, more preferably 60 mass % or greater, even more preferably 70mass % or greater, even more preferably 80 mass % or greater, andparticularly preferably 85 mass % or greater with respect to the totalsolid content of the ink composition. The upper limit of the total solidcontent of the gel particles may be 100 mass % with respect to the totalsolid content of the ink composition. In a case where the inkcomposition includes solid components other than the gel particles, theupper limit thereof is preferably 99 mass % or less and more preferably95 mass % or less.

The ink composition contains water, but the amount of water is notparticularly limited. Among these, a content of water is preferably 10mass % to 99 mass, more preferably 20 mass % to 95 mass %, even morepreferably 30 mass % to 90 mass %, and even more preferably 50 mass % to90 mass % with respect to the total mass of the ink composition.

(Colorant)

The ink composition contains at least one colorant.

The colorant is not particularly limited and can be arbitrarily selectedfrom well-known color materials such as a pigment, a water-soluble dye,and a dispersed dye. Among these, in view of excellent weatherresistance and opulent color reproducibility, the colorant morepreferably includes a pigment.

—Pigment—

The pigment is not particularly limited, and can be appropriatelyselected depending on the purposes. Examples of the pigment includewell-known organic pigments and inorganic pigments, and also includeresin particles colored with a dye, a commercially available pigmentdispersion, or a surface-treated pigment (for example, a dispersionobtained by dispersing a pigment as a dispersion medium in water, aliquid organic compound, or an insoluble resin and a dispersion obtainedby treating a pigment surface with a resin or a pigment derivative).

Examples of the organic pigment and the inorganic pigment include ayellow pigment, a red pigment, a magenta pigment, a blue pigment, a cyanpigment, a green pigment, an orange pigment, a violet pigment, a brownpigment, a black pigment, and a white pigment.

As the yellow pigment, monoazo pigments such as C. I. Pigment yellow 1,2, 3, 4, 5, 10, 65, 73, 74, 75, 97, 98, 111, 116, 130, 167, and 205,monoazo lake pigments such as 61, 62, 100, 168, 169, 183, 191, 206, 209,and 212, disazo pigments such as 12, 13, 14, 16, 17, 55, 63, 77, 81, 83,106, 124, 126, 127, 152, 155, 170, 172, 174, 176, 214, and 219, ananthraquinone pigment such as 24, 99, 108, 193, and 199,monoazopyrazolone pigments such as 60, condensed azo pigments such as93, 95, 128, and 166, isoindoline pigments such as 109, 110, 139, 173,and 185, benzimidazolone pigments such as 120, 151, 154, 175, 180, 181,and 194, azomethine metal complex pigments such as 117, 129, 150, and153, quinophthalone pigments such as 138, and quinoxaline pigments suchas 213 are preferable.

As the red pigment or the magenta pigment, monoazo lake pigments such asC. I. Pigment red 193, disazo pigments such as 38, naphthol AS pigmentssuch as 2, 5, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 22, 23, 31, 32, 112,114, 146, 147, 150, 170, 184, 187, 188, 210, 213, 238, 245, 253, 256,258, 266, 268, and 269, β-naphthol pigments such as 3, 4, and 6,β-naphthol lake pigments such as 49, 53, and 68, naphthol AS lakepigments such as 237, 239, and 247, pyrazolone pigments such as 41, BONAlake pigments such as 48, 52, 57, 58, 63, 64:1, and 200, xanten lakepigments such as 81:1, 169, and 172, thioindigo pigments such as 88,181, and 279, perylene pigments such as 123, 149, 178, 179, 190, and224, condensed azo pigments such as 144, 166, 214, 220, 221, 242, and262, anthraquinone pigments such as 168, 177, 182, 226, and 263,anthraquinonelake pigments such as 83, benzimidazolone pigments such as171, 175, 176, 185, and 208, quinacridone pigments such as 122, 202(including a mixture with C. I. Pigment violet 19), 207, and 209,diketopyrrolopyrrole pigments such as 254, 255, 264, 270, and 272, andazomethine metal complex pigments such as 257 and 271 are preferable.

As the blue pigment or the cyan pigment, naphthol AS pigments such as C.I. Pigment blue 25, and 26, phthalocyanine pigments such as 15, 15:1,15:2, 15:3, 15:4, 15:6, 16, 17:1, 75, and 79, dyeing lake pigments suchas 1, 24:1, 56, 61, and 62, anthraquinone-based pigments such as 60,indigo pigments such as 63, and dioxazine pigments such as 80 arepreferable.

As the green pigment, dyeing lake pigments such as C. I. Pigment green 1and 4, phthalocyanine pigments such as 7 and 36, and azomethine metalcomplex pigments such as 8 are preferable.

As the orange pigment, monoazo pigments such as C. I. Pigment orange 1,β-naphthol pigments such as 2, 3, and 5, naphthol AS pigments such as 4,24, 38, and 74, pyrazolone pigments such as 13 and 34, benzimidazolonepigments such as 36, 60, 62, 64, and 72, disazo pigments such as 15 and16, β-naphthollake pigments such as 17 and 46, naphthalenesulfonic acidlake pigments such as 19, perinone pigments such as 43, quinacridonepigments such as 48 and 49, anthraquinone-based pigments such as 51,isoindolinone pigments such as 61, isoindoline-based pigments such as66, azomethine metal complex pigments such as 68, anddiketopyrrolopyrrole pigments such as 71, 73, and 81 are preferable.

As the brown pigment, BONA lake pigments such as C. I. Pigment Brown 5,condensed azo pigments such as 23, 41, and 42, and benzimidazolonepigments such as 25 and 32 are preferable.

As the violet pigment, dyeing lake pigments such as C. I. pigment violet1, 2, 3 and 27, naphthol AS pigments such as 13, 17, 25 and 50,anthraquinone lake pigments such as 5:1, quinacridone pigments such as19, dioxazine pigments such as 23 and 37, perylene pigments such as 29,benzimidazolone pigments such as 32, and thioindigo pigments such as 38are preferable.

As the black pigment, indazine pigments such as C. I. Pigment black 1,carbon black which is 7, graphite which is 10, magnetite which is 11,anthraquinone pigments such as 20, and perylene pigments such as 31 and32 are preferable.

As the white pigment, zinc oxide which is C. I. Pigment white 4,titanium oxide which is 6, zinc sulfide which is 7, zirconium oxide(zirconium white) which is 12, calcium carbonate which is 18, aluminumoxide·silicon oxide (kaolin clay) which is 19, barium sulfate which is21 or 22, aluminum hydroxide (alumina white) which is 23, silicon oxidewhich is 27, and calcium silicate which is 28 are preferable.

The inorganic particles used in the white pigment may be a singlesubstance, or may be oxide of silicon, aluminum, zirconium, titanium,and the like, or composite particles with an organic metal compound oran organic compound.

It is preferable that selection of a pigment, a dispersing agent, and amedium, a dispersion condition, and a filtration condition are set suchthat a volume average particle diameter of the pigment particles ispreferably 0.005 μm to 0.5 μm, more preferably 0.01 μm to 0.45 μm, evenmore preferably 0.015 μm to 0.4 μm.

The volume-average particle diameter and the particle size distributionof the pigment particles are obtained by using a commercially availableparticle diameter measuring device such as a wet-type particle sizedistribution measuring device LA-910 (manufactured by Horiba Ltd.) andmeasuring a volume average particle diameter by the dynamic lightscattering method.

—Water-Soluble Dye—

Examples of the water-soluble dye include an acid dye or a direct dye.The acid dye and the direct dye have structures having acidic groups asa solubilizing group. Examples of the acidic group include a sulfonicacid group and a salt thereof, a carboxylic acid group and a saltthereof, and a phosphoric acid group and a salt thereof. One acidicgroup or a plurality of acidic groups may be included, or the acidicgroups may be combined. Examples of the chemical structure ofchromophore contained in the water-soluble dye include azo-based,phthalocyanine-based, triphenylmethane-based, xanthene-based,pyrazolone-based, nitro-based, stilbene-based, quinoline-based,methine-based, thiazole-based, quinoneimine-based, indigoid-based,rhodamine-based, and anthraquinone-based structures.

The content of the colorant in the ink composition can be appropriatelyselected. However, the content is preferably 0.1 mass % to 30 mass % andmore preferably 0.5 mass % to 20 mass % with respect to the total massof the ink composition.

—Dispersing Agent—

In a case where a pigment is used as a colorant, when the pigmentparticles are prepared, a pigment dispersing agent may be used ifnecessary. Examples of the pigment dispersing agent that can be usedinclude an active agent such as a higher fatty acid salt, alkyl sulfate,alkyl ester sulfate, alkyl sulfonate, sulfosuccinate, naphthalenesulfonate, alkyl phosphate, polyoxyalkylene alkyl ether phosphate,polyoxyalkylene alkyl phenyl ether, polyoxy ethylene polyoxypropyleneglycol, glycerin ester, sorbitan ester, polyoxyethylene fatty acidamide, and amine oxide, a block copolymer consisting of two or moremonomers selected from styrene, a styrene derivative, a vinylnaphthalenederivative, acrylic acid, acrylic acid derivative, maleic acid, maleicacid derivative, itaconic acid, an itaconic acid derivative, fumaricacid, and a fumaric acid derivative, a random copolymer, and saltsthereof.

As the dispersion method of the pigment, for example, various dispersingdevices such as a ball mill, a sand mill, an attritor, a roll mill, anagitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, apearl mill, a wet-type jet mill, and a paint shaker can be used. For thepurpose of removing coarse fraction of the pigment dispersion, acentrifugal separator, and a filter are preferably used.

Components other than the components described above can be added to theink composition, if necessary. Hereinafter, the other components aredescribed.

(Sensitizing Agent)

It is preferable to add a sensitizing agent to the ink composition, inorder to promote the decomposition by the functional groups thatgenerate radicals by irradiation with active energy rays due to activeenergy rays irradiation, which the gel particles have. The sensitizingagent absorbs specific active energy rays and is in an electron excitedstate. The sensitizing agent that is in the electron excited state comesinto contact with the functional groups that generate radicals byirradiation with active energy rays, generates actions such as electronmovement, energy movement, or heat generation, and promotes chemicalchanges of the functional groups that generate radicals by irradiationwith active energy rays, that is, decomposition and generation ofradicals.

Examples of the well-known sensitizing agents that can be used togetherinclude benzophenone, thioxanthone, especially isopropylthioxanthone,anthraquinone, and a 3-acylcoumarin derivative, terphenyl, styrylketone,and 3-(aroylmethylene) thiazoline, camphorquinone, eosin, rhodamine, anderythrosine. Compounds represented by Formula (i) disclosed inJP2010-24276A or compounds represented by Formula (I) disclosed inJP1994-107718A (JP-H06-107718A) can be suitably used.

Among these, in view of suitability to LED light and reactivity with thefunctional groups that generate radicals by irradiation with activeenergy rays, as the sensitizing agent, at least one selected fromthioxanthone, isopropylthioxanthone, and benzophenone is preferable, atleast one selected from thioxanthone and isopropylthioxanthone is morepreferable, and isopropylthioxanthone is even more preferable.

In a case where the ink composition contains a sensitizing agent, thesensitizing agent may be contained singly, or two or more types thereofmay be contained in combination.

In a case where the ink composition contains the sensitizing agent, inview of improving reactivity with the functional groups that generateradicals by irradiation with active energy rays, the sensitizing agentmay be included in the gel particles in a range of not deteriorating theeffect of the embodiment of the invention.

In a case where the ink composition contains the sensitizing agent, thecontent of the sensitizing agent is preferably 0.1 mass % to 25 mass %with respect to the total mass of the ink composition.

(Polymerization Inhibitor)

In view of increasing storability, a polymerization inhibitor may beadded. Examples of the polymerization inhibitor include p-methoxyphenol,hydroquinone, and methoxybenzoquinone, quinones such as phenothiazine,catechols, alkylphenols, alkylbisphenols, zinc dimethyldithiocarbamate,copper dimethyldithiocarbamate, copper dibutyldithiocarbamate, coppersalicylate, thiodipropionate esters, mercaptobenzimidazole, andphosphites. p-Methoxyphenol, catechols, and quinones are preferable, andhydroquinone, benzoquinone, p-methoxyphenol, TEMPO, TEMPOL, cupferronAl, a tris(N-nitroso-N-phenylhydroxylamine)aluminum salt, and the likeare more preferable.

(Ultraviolet Absorbing Agent)

In view of improvement of the weather resistance and fading preventionof the obtained film, an ultraviolet absorbing agent may be used in theink composition.

Examples of the ultraviolet absorbing agent include the well-knownultraviolet absorbing agent, for example, a benzotriazole-basedcompound, a benzophenone-based compound, a triazine-based compound, anda benzoxazole-based compound.

(Organic Solvent)

In order to improve adhesiveness of the recording medium, organicsolvents as follows may be added to the ink composition.

-   -   Alcohols (for example, methanol, ethanol, propanol, isopropanol,        butanol, isobutanol, secondary butanol, tertiary butanol,        pentanol, hexanol, cyclohexanol, and benzyl alcohol),    -   Polyhydric alcohols (for example, ethylene glycol, diethylene        glycol, triethylene glycol, polyethylene glycol, propylene        glycol, dipropylene glycol, polypropylene glycol, butylene        glycol, hexanediol, pentanediol, glycerin, hexanetriol,        thiodiglycol, and 2-methyl propanediol),    -   Polyhydric alcohol ethers (for example, ethylene glycol        monomethyl ether, ethylene glycol monoethyl ether, ethylene        glycol monobutyl ether, diethylene glycol monoethyl ether,        diethylene glycol monomethyl ether, diethylene glycol monobutyl        ether, propylene glycol monomethyl ether, propylene glycol        monobutyl ether, tripropylene glycol monomethyl ether,        dipropylene glycol monomethyl ether, dipropylene glycol dimethyl        ether, ethylene glycol monomethyl ether acetate, triethylene        glycol monomethyl ether, triethylene glycol monoethyl ether,        triethylene glycol monobutyl ether, ethylene glycol monophenyl        ether, and propylene glycol monophenyl ether),    -   Amines (for example, ethanolamine, diethanolamine,        triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine,        morpholine, N-ethylmorpholine, ethylenediamine,        diethylenediamine, triethylenetetramine, tetraethylenepentamine,        polyethyleneimine, pentamethyl diethylenetriamine, and        tetramethylpropylenediamine),    -   Amides (for example, formamide, N,N-dimethylformamide, and        N,N-dimethylacetamide),    -   Heterocyclic rings (for example, 2-pyrrolidone,        N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, 2-oxazolidone,        1,3-dimethyl-2-imidazolidinone, and γ-butyrolactone)    -   Sulfoxides (for example, dimethylsulfoxide),    -   Sulfones (for example, sulfolane),    -   Other (urea, acetonitrile, and acetone)

The content of the solvent is preferably 1 mass % to 30 mass % and ismore preferably added in the range of 1 mass % to 20 mass % with respectto the total mass of the ink composition.

(Surfactant)

A surfactant may be added to the ink composition. The surfactant used inthe ink composition is differentiated from a surfactant used when thegel particles are produced.

Examples of the surfactant include surfactants disclosed inJP1987-173463A (JP-S62-173463A) and JP1987-183457A (JP-S62-183457A).Examples thereof include nonionic surfactants such as polyoxyethylenealkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols,polyoxyethylene, polyoxypropylene block copolymers, and siloxanes.

Instead of the surfactant, organic fluoro compounds may be used.

The organic fluoro compound is preferably hydrophobic. Examples of theorganic fluoro compound include a fluorine-based surfactant, an oilyfluorine-based compound (for example, fluorine oil), and a solid-likefluorine compound resin (for example, tetrafluoroethylene resin) andexamples thereof include organic fluoro compounds disclosed inJP1982-9053B (JP-S57-9053B) (Sections 8 to 17), JP1987-135826A(JP-562-135826A).

In view of film properties, adhesiveness, and jettability control, theink composition may contain a polymerizable compound, a water-solubleresin, and a water dispersible resin outside the gel particles, ifnecessary.

The expression “the ink composition contains a polymerizable compoundoutside the gel particles” means that the ink composition contains apolymerizable compound that is not included in the gel particles. Thesame is applied to a case where the water-soluble resin and the waterdispersible resin are contained outside the gel particles.

(Polymerizable Compound that can be Contained Outside the Gel Particles)

The ink composition preferably contains the polymerizable compoundoutside the gel particles.

If the ink composition contains the polymerizable compound outside gelparticles, crosslinking efficiency between gel particles can beimproved, and a film having higher film hardness can be formed.Crosslinking highly efficiently proceeds with respect to active energyrays (light) having low exposure illuminance (for example, 40 mJ/cm² to70 mJ/cm²).

Examples of the polymerizable compound include compounds havingethylenically unsaturated groups and radical polymerizable compoundssuch as acrylonitrile, styrene, unsaturated polyester, unsaturatedpolyether, unsaturated polyamide, and unsaturated urethane.

Among these, as the polymerizable compound, a compound having anethylenically unsaturated group is preferable, and a compound having a(meth)acryloyl group is particularly preferable. The polymerizablecompound is preferably water-soluble or water dispersible polymerizablecompounds.

The expression “water-soluble” means properties in which in a case wherethe compound is dried at 105° C. for two hours, a dissolution amount to100 g of distilled water at 25° C. exceeds 1 g.

The expression “water dispersible” means properties which are waterinsoluble and dispersed in water. Here, the expression “water insoluble”means that in a case where the compound is dried at 105° C. for twohours, a dissolution amount to 100 g of distilled water at 25° C. is 1 gor less.

In view of water solubility or water dispersibility, as thepolymerizable compound, a compound having at least one selected from anamide structure, a polyethylene glycol structure, a polypropylene glycolstructure, a carboxyl group, and a salt of a carboxy group ispreferable.

In view of the water solublility or water dispersibility, as thepolymerizable compound that can be contained outside the gel particles,for example, at least one selected from (meth)acrylic acid, sodium(meth)acrylate, potassium (meth)acrylate, N,N-dimethylacrylamide,N,N-diethylacrylamide, morpholine acrylamide, N-2-hydroxyethyl(meth)acrylamide, N-vinyl pyrrolidone, N-vinyl caprolactam,2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate,2-hydroxypropyl (meth)acrylate, glycerin monomethacrylate,N-[tris(3-acryloylaminopropyloxymethylene)methyl]acrylamide, diethyleneglycol bis(3-acryloylaminopropyl) ether, polyethylene glycoldi(meth)acrylate, polypropylene glycol di(meth)acrylate, a compoundrepresented by Formulae (a) to (d) below, and ethoxylatedtrimethylolpropane triacrylate (for example, SR9035 manufactured bySartomer) is preferable, and at least one selected from (meth)acrylicacid, N,N-dimethylacrylamide, N-2-hydroxyethyl (meth)acrylamide,2-hydroxyethyl (meth)acrylate, glycerin monomethacrylate,N-[tris(3-acryloylaminopropyloxymethylene)methyl]acrylamide, diethyleneglycol bis(3-acryloylaminopropyl) ether, polyethylene glycoldi(meth)acrylate, and polypropylene glycol di(meth)acrylate, a compoundrepresented by Formulae (a) to (d) below, and ethoxylatedtrimethylolpropane triacrylate (for example, SR9035 manufactured bySartomer) is more preferable.

In Formula (a), a plurality of R¹'s each independently represent ahydrogen atom, an alkyl group, an aryl group, or a heterocyclic ringgroup, a plurality of R²'s each independently represent a hydrogen atomor a methyl group, and a plurality of L¹'s each independently representa single bond or a divalent linking group.

In Formula (b), a plurality of R³'s each independently represent ahydrogen atom or a methyl group, a plurality of L²'s each independentlyrepresent an alkylene group having 1 to 8 carbon atoms, a plurality ofk's and p's each independently represent 0 or 1, and a plurality of meach independently represent an integer of 0 to 8. Here, at least one ofk or p is 1.

In Formula (c), a plurality of R⁴ each independently represent ahydrogen atom or a methyl group, a plurality of n's each independentlyrepresent an integer of 1 to 8, and 1 represents an integer of 0 or 1.

In Formula (d), Z¹ represents a residue obtained by q hydrogen atomsfrom a hydroxyl group of polyol, q represents an integer of 3 to 6, aplurality of R⁵ each independently represent a hydrogen atom or a methylgroup, a plurality of C's each independently represent an alkylene grouphaving 1 to 8 carbon atoms.

Specific examples of the compound represented by Formulae (a) to (d)include compounds represented by AM-1 to AM-4 below.

AM-1 to AM-4 can be synthesized by the method disclosed in JP05591858B.

(Water-Soluble Resin or Water Dispersible Resin that can be ContainedOutside the Gel Particles)

The structures of the water-soluble resin or the water dispersible resinare not particularly limited, and may be any structures. Examples of thewater-soluble resin or the water dispersible resin include structuressuch as a chain-shaped structure, a ramified (branched) structure, astar-shaped structure, a crosslinked structure, and a mesh-shapedstructure.

The expression “water-soluble” in the water-soluble resin has the samemeaning as that of the expression “water-soluble” in the “water-solublepolymerizable compound”, and the expression “water dispersible” in thewater dispersible resin has the same meaning as that of the expression“water dispersible” in the “water dispersible polymerizable compound”.

As the water-soluble resin or the water dispersible resin, a resinhaving a functional group selected from a carboxyl group, a salt of acarboxy group, a sulfo group, a salt of a sulfo group, a sulfuric acidgroup, a salt of a sulfuric acid group, a phosphonic acid group, a saltof a phosphonic acid group, a phosphoric acid group, a salt of aphosphoric acid group, an ammonium base, a hydroxyl group, a carboxylicacid amide group, and an alkyleneoxy group is preferable.

As the counter cation of the salt, an alkali metal cation such as sodiumand potassium, an alkali earth metal cation such as calcium andmagnesium, an ammonium cation, or a phosphonium cation is preferable, analkali metal cation is particularly preferable.

As an alkyl group included in an ammonium group of an ammonium base, amethyl group or an ethyl group is preferable.

As the counter anion of the ammonium base, a halogen anion such aschlorine and bromine, a sulfate anion, a nitrate anion, a phosphateanion, a sulfonate anion, a carboxylate anion, or a carbonate anion ispreferable, and a halogen anion, a sulfonate anion, or a carbonate anionis particularly preferable.

As a substituent on the nitrogen atom of the carboxylic acid amidegroup, an alkyl group having 8 or less carbon atoms is preferable, andan alkyl group having 6 or less carbon atoms is particularly preferable.

The resin having an alkyleneoxy group preferably has an alkyleneoxychain consisting of repetition of an alkyleneoxy group. The number ofthe alkyleneoxy groups included in the alkyleneoxy chain is preferably 2or greater and particularly preferably 4 or greater.

˜Preferably Physical Properties of Ink Composition˜

In a case where the ink composition is set as 25° C. to 50° C., the inkcomposition preferably has a viscosity of 3 mPa·s to 15 mPa·s and morepreferably has a viscosity of 3 mPa·s to 13 mPa·s. Particularly, as theink composition, the viscosity of the ink composition at 25° C. ispreferably 50 mPa·s or less. If the viscosity of the ink composition isin the range described above, high jetting stability in a case where theink composition is applied to the ink jet recording can be realized. Theviscosity change of the ink composition in a case where the inkcomposition is applied to the ink jet recording gives great influence ona change of liquid droplet sizes and a change of a liquid dropletejection rate and thus generates image quality deterioration.Accordingly, it is required that the temperature of the ink compositionat the time of ejection is constantly maintained. Accordingly, it isappropriate that the control width of the temperature of the inkcomposition is preferably ±5° C. of a set temperature, more preferably±2° C. of a set temperature, and even more preferably ±1° C. of a settemperature.

The viscosity of the ink composition is measured by using a viscometer:VISCOMETER TV-22 (manufactured by Toki Sangyo Co., Ltd.).

<Photosensitive Composition>

The photosensitive composition has the polymerizable group and thefunctional groups that generate radicals by irradiation with activeenergy rays and contains gel particles having a three-dimensionalcrosslinked structure including at least one bond selected from aurethane bond and a urea bond, and water.

As the gel particles and water in the photosensitive composition, thesame gel particles and water used in the ink composition can be used.

In order to cause the gel particles according to the embodiment of theinvention to be contained, the photosensitive composition suppresses theoccurrence of the migration of the low molecular weight components andthus a film having excellent film hardness can be obtained.

In view of the film hardness, it is preferable that the photosensitivecomposition further contains the polymerizable compound outside the gelparticles.

Since the film formed by the irradiation of the active energy rays hasexcellent film hardness, the photosensitive composition can be suitablyused in various uses such as a coating agent, an adhesive, and a paint,starting from the use as the ink composition.

<Method of Producing Water Dispersion of Gel Particles>

The method of producing water dispersion of the gel particles is notparticularly limited, as long as water dispersion of gel particlesincluding gel particles having the configurations described above andwater can be produced.

In view of easily obtaining water dispersion of the gel particles, amethod of producing water dispersion of the gel particles according tothe embodiment described below is preferable as a method of producingwater dispersion of the gel particles.

A method of producing water dispersion of the gel particles according tothe embodiment (hereinafter, referred to as a “producing method of theembodiment”) includes an emulsification step of obtaining an emulsion bymixing and emulsifying any one oil phase component selected from an oilphase component (hereinafter, referred to as the “oil phase componentA”) including a trifunctional or higher isocyanate compound having afunctional groups that generate radicals by irradiation with activeenergy rays, a polymerizable monomer, and an organic solvent, an oilphase component (hereinafter, referred to as the “oil phase componentB”) including a trifunctional or higher isocyanate compound having afunctional groups that generate radicals by irradiation with activeenergy rays, a trifunctional or higher isocyanate compound having apolymerizable group, and an organic solvent, an oil phase component(hereinafter, referred to as the the “oil phase component C”) includingan trifunctional or higher isocyanate compound having a polymerizablegroup and a functional groups that generate radicals by irradiation withactive energy rays, a polymerizable monomer, and an organic solvent, andan oil phase component (hereinafter, referred to as the “oil phasecomponent D”) including a trifunctional or higher isocyanate compoundhaving a functional groups that generate radicals by irradiation withactive energy rays, a trifunctional or higher isocyanate compound havinga polymerizable group, a polymerizable monomer, and an organic solventand a water phase component including water; and a gelation step gellingthe emulsion by heating.

In view of easily producing water dispersion of the gel particles, theoil phase component A, the oil phase component B, and the oil phasecomponent D are preferable as the oil phase component.

If necessary, the producing method of the embodiment may have othersteps.

According to the producing method of the embodiment, water dispersion ofthe gel particles described above can be easily produced.

Hereinafter, respective steps in the producing method of the embodimentare specifically described.

Specific examples of the components used in the respective steps, andpreferable aspects are as described in the section of the gel particles,and thus the descriptions thereof are omitted.

(Emulsification Step)

The emulsification step is a step of obtaining an emulsion by mixing andemulsifying any one oil phase component selected from the oil phasecomponent A, the oil phase component B, the oil phase component C, andthe oil phase component D, and a water phase component including water.

In the emulsification step, if, any one oil phase component selectedfrom the oil phase component A including a trifunctional or higherisocyanate compound having a functional group that generates radicals byirradiation with active energy rays, a polymerizable monomer, and anorganic solvent, the oil phase component B including a trifunctional orhigher isocyanate compound having a functional groups that generatesradicals by irradiation with active energy rays, a trifunctional orhigher isocyanate compound having a polymerizable group, and an organicsolvent, the oil phase component C including a trifunctional or higherisocyanate compound having a polymerizable group and a functional groupthat generates radicals by irradiation with active energy rays, apolymerizable monomer, and an organic solvent, and the oil phasecomponent D including a trifunctional or higher isocyanate compoundhaving a functional group that generates radicals by irradiation withactive energy rays, a trifunctional or higher isocyanate compound havinga polymerizable group, a polymerizable monomer, and an organic solventis used as the oil phase component, the gel particles having apolymerizable group and a functional group that generates radicals byirradiation with active energy rays can be finally obtained at least onthe surface or on the surface and near the surface.

It is considered that the trifunctional or higher isocyanate compoundshaving the polymerizable monomers that the oil phase component A, theoil phase component B, the oil phase component C, and the oil phasecomponent D include and the polymerizable groups that the oil phasecomponent B, the oil phase component C, and the oil phase component Dinclude become polymerizable groups existing on the surfaces of the gelparticles or on the surfaces or the portions near the surfaces.

Examples of the organic solvent included in the oil phase componentinclude ethyl acetate and methyl ethyl ketone.

In addition to the components, the oil phase component may include othercomponents, if necessary.

Examples of the other components include the compound having hydrophilicgroups.

If the oil phase component includes the compound having the hydrophilicgroup, it is possible to obtain gel particles having hydrophilic groupson the surfaces thereof.

The trifunctional or higher isocyanate compound is as described in thesection of the gel particles. Among these, the trifunctional or higherisocyanate compound is preferably an isocyanate compound derived from atleast one selected from isophorone diisocyanate, hexamethylenediisocyanate, trimethylhexamethylene diisocyanate,1,3-bis(isocyanatomethyl) cyclohexane, m-xylylene diisocyanate, anddicyclohexylmethane 4,4′-diisocyanate.

The water phase component may include other components in addition towater, if necessary.

In a case where the oil phase component includes the compound having atleast one hydrophilic group selected from a carboxy group, a sulfogroup, a sulfonic acid group, a phosphonic acid group, and a phosphoricacid group as the compound having the hydrophilic group, the water phasecomponent may include a neutralizing agent.

If the oil phase component includes the compound having hydrophilicgroups, and the water phase component includes the neutralizing agent,the hydrophilic groups such as a carboxy group are neutralized by mixingthe oil phase component and the water phase component so as to form asalt of the carboxy group or the like. The formed salt also functions asthe hydrophilic group of the gel particles. These salts haveparticularly excellent effect of dispersing gel particles in water.

Examples of the neutralizing agent include sodium hydroxide.

According to the producing method of the embodiment, as a raw materialfor forming gel particles in the three-dimensional crosslinked structureincluding at least one bond selected from a urethane bond and a ureabond due to reaction with the isocyanate group, in addition to water,the polyfunctional alcohol, polyfunctional phenol, polyfunctional aminehaving hydrogen atoms on nitrogen atoms, polyfunctional thiol, and thelike may be used.

Specific examples thereof include compounds such as polyfunctionalalcohol (for example, propylene glycol, glycerin, andtrimethylolpropane), polyfunctional amine (for example,bis(hexamethylene) triamine, ethylenediamine, and diethylenetriamine),and polyfunctional thiol (for example, pentaerythritoltetra(3-mercaptopropionate)), and polyfunctional alcohol is particularlypreferable.

These compounds may be used singly and two or more types thereof may beused in combination. These compounds are added to the oil phasecomponent and/or the water phase component according to the solubilitythereof.

According to the producing method of the embodiment, in addition to theraw materials, a surfactant is preferably used. Examples of thesurfactant include the surfactant.

Generally, it is considered that a surfactant having a comparativelylong-chained hydrophobic group is excellent as the surfactant used inthe emulsification. For example, as the surfactant, surfactantsdisclosed in “Surfactant Handbook” (Ichiro Nishi et al., published bySangyo Tosho Co., Ltd., 1980). Specifically, an alkali metal salt suchas an alkyl sulfuric acid salt, alkyl sulfonic acid, and alkyl benzenesulfonic acid is preferable, and an alkyl sulfuric acid ester salt ismore preferable.

In view of dispersion stability, an alkyl chain length of an alkylsulfuric acid ester salt is preferably 12 or greater and more preferably16 or greater.

Examples of the surfactant include a sodium salt and a polycarboxylicacid salt of an aromatic sulfonic acid formalin condensate such as asodium naphthalenesulfonate formalin condensate which is a polymer-typesurfactant and polyoxyethylene-1-(allyloxymethyl) alkyl ether sulfateand polyoxyethylene nonyl propenyl phenyl ether sulfate which arereactive surfactants.

The polymer-type surfactant and the reactive surfactant can beparticularly suitably used, in view of suppression of the migration.

The surfactant may be added to any one of the oil phase component andthe water phase component, but the surfactant generally has lowsolubility to the organic solvent, and thus is added to the water phasecomponent.

The amount of the surfactant is preferably 0.1 mass % to 5 mass % andmore preferably 0.5 mass % to 3 mass % with respect to a total solidcontent of the oil phase component.

The total amount (hereinafter, referred to as a “total solid content”)obtained by excluding the organic solvent and water from the oil phasecomponent and the water phase component in the emulsification stepcorresponds to the total solid content of the produced gel particles.

The amount of the trifunctional or higher isocyanate compound having thefunctional groups that generate radicals by irradiation with activeenergy rays in the oil phase component is not particularly limited andis preferably, for example, 0.1 mass % to 25 mass % with respect to thetotal solid content.

The amount of the trifunctional or higher isocyanate compound having thepolymerizable group in the oil phase component is not particularlylimited and is preferably, for example, 10 mass % to 70 mass % withrespect to the total solid content.

The amount of the trifunctional or higher isocyanate compound having thepolymerizable group and the functional groups that generate radicals byirradiation with active energy rays in the oil phase component is notparticularly limited, and is preferably, for example, 0.1 mass % to 25mass % with respect to a total solid content.

In a case where the oil phase component includes the polymerizablemonomer, the amount of the polymerizable monomer in the oil phasecomponent is not particularly limited and is preferably, for example,0.1 mass % to 75 mass % with respect to the total solid content.

The amount of the organic solvent is not particularly limited and isappropriately depending on types and amounts of the components and thelike included in the oil phase component.

The amount of water is not particularly limited and is appropriatelyselected depending on types and amounts of the components and the likeincluded in the oil phase component.

In a case where the oil phase component includes the compound having thehydrophilic group, an amount of the compound having the hydrophilicgroup in the oil phase component is not particularly limited and ispreferably, for example, 0.1 mass % to 40 mass % with respect to thetotal solid content.

The respective components included in the oil phase component may besimply mixed, all the components may be mixed together, or respectivecomponents may be divided into several groups to be mixed.

The method of mixing the oil phase component and the water phasecomponent is not particularly limited, and examples thereof includemixture by stirring.

The method of emulsifying the mixture obtained by mixing is notparticularly limited, and examples thereof include emulsification by anemulsification device (for example, disperser) such as a homogenizer.

The rotation speed of the disperser in the emulsification is, forexample, 5,000 rpm to 20,000 rpm and preferably 10,000 rpm to 15,000rpm.

The rotation time of the emulsification is, for example, 1 minute to 120minutes, preferably 3 minutes to 60 minutes, more preferably 3 minutesto 30 minutes, and even more preferably 5 minutes to 15 minutes.

(Gelation Step)

The gelation step is a step of gelling the emulsion by heating.

In the gelation step, trifunctional or higher isocyanate compound andwater react with each other by heating the emulsion, the isocyanategroups are crosslinked to each other, so as to obtain a dispersionliquid containing gel particles having the three-dimensional crosslinkedstructure including at least one selected from a urethane bond and aurea bond, the polymerizable group, and the functional groups thatgenerate radicals by irradiation with active energy rays.

The heating temperature (reaction temperature) of the emulsion in thegelation step is preferably 35° C. to 70° C. and more preferably 40° C.to 60° C.

The heating time (reaction time) in the gelation step is preferably 6hours to 50 hours, more preferably 12 hours to 40 hours, and even morepreferably 15 hours to 35 hours.

The gelation step preferably includes a step of distilling an organicsolvent from an emulsion.

(Mixture Step)

The mixture step may have a step of mixing gel particles that can beobtained in the gelation step, water, and a colorant. The method ofmixing the gel particles, water, and a colorant is not particularlylimited. The gel particles may be used in a dispersion liquid state.

The colorant is as described as the colorant containing water dispersionin gel particles.

The producing method of the embodiment may have other steps in additionto the emulsification step, the gelation step, and the mixture step, ifnecessary.

Examples of the other steps include a step of adding other components.

The other added components are as described above as the othercomponents that can contain the water dispersion of the gel particles.

The water dispersion of the gel particles produced in the method ofproducing the water dispersion of the gel particles can be suitably usedin an ink composition, a coating agent, an adhesive, a paint, and thelike.

<Image Forming Method>

The image forming method includes an ink applying step of applying theink composition on the recording medium and an irradiation step ofirradiating the ink composition applied on the recording medium withactive energy rays. If these steps are performed, a film (for example,an image) by the ink composition fixed on the recording medium isformed.

(Ink Applying Step)

Hereinafter, the ink applying step in the the image forming method isdescribed.

The ink applying step is not particularly limited, as long as the inkapplying step is a step of applying the ink composition on the recordingmedium.

As an aspect of applying the ink composition on the recording medium, anaspect of applying the ink composition on the recording medium by an inkjet method is particularly preferable.

In the image forming method, an ink jet recording device used in a casewhere the ink applying step of the ink jet method is applied is notparticularly limited, a well-known ink jet recording device that canachieve a desired resolution can be arbitrarily selected to be used.That is, all well-known ink jet recording devices including commerciallyavailable products can eject the ink composition to the recording mediumin the image forming method.

Examples of the ink jet recording device include devices including anink supplying method, a temperature sensor, and heating means.

The ink supplying method consists of, for example, an original tankincluding the ink composition, a supply piping, an ink supply tank justbefore an ink jet head, a filter, and a piezo-type ink jet head. Thepiezo-type ink jet head can be driven so as to eject multi-sized dots ofpreferably 1 pl to 100 pl and more preferably 8 pl to 30 pl at aresolution of preferably 320 dpi×320 dpi to 4,000 dpi×4,000 dpi (dot perinch), more preferably 400 dpi×400 dpi to 1,600 dpi×1,600 dpi, and evenmore preferably 720 dpi×720 dpi. The dpi represents the number of dotsper 2.54 cm (1 inch).

In the ink applying step, since it is desired that the ejected inkcomposition have a constant temperature, the ink jet recording devicepreferably includes stabilizing means in an ink composition temperature.A piping method from the ink tank (an intermediate tank in a case wherethe intermediate tank exists) to a nozzle exit surface, that is, allmembers become targets as portions to have the constant temperature.That is, heat insulation and heating can be performed from the the inksupply tank to the ink jet head portion.

A method of controlling the temperature is not particularly limited,but, for example, it is preferable to perform heating control dependingon the flow rate of the ink composition and ambient temperature, forexample, by providing temperature sensors on respective piping portions.The temperature sensor can be provided in an ink supply tank and aportion near a nozzle of an ink jet head. It is preferable that the headunit to be heated is thermally blocked or heat insulated such that themain body of the device is not influenced by the temperature from theexternal air. In order to reduce the printer startup time required forthe heating or in order to reduce the loss of heat energy, it ispreferable to reduce the heat capacity of the entire heating unittogether with performing heat insulation from other portions.

The recording medium is not particularly limited, and well-knownrecording mediums can be used as a support or a recording material. Asthe recording medium, for example, paper, paper on which plastic (forexample, polyethylene, polypropylene, and polystyrene) is laminated, ametal plate (for example, aluminum, zinc, and copper), a plastic film(for example, a polyvinyl chloride resin, cellulose diacetate, cellulosetriacetate, cellulose propionate, cellulose butyrate, cellulose acetatebutyrate, cellulose nitrate, polyethylene terephthalate, polyethylene,polystyrene, polypropylene, polycarbonate, and polyvinyl acetal), andpaper or a plastic film obtained by laminating and vapor depositingmetal described above.

Among these, since the ink composition have excellent adhesiveness, theink composition can be suitably used in a nonabsorbable recording mediumas a recording medium. A plastic base material such as polyvinylchloride, polyethylene terephthalate, and polyethylene is preferable, apolyvinyl chloride resin base material is more preferable, and apolyvinyl chloride resin sheet or film is even more preferable.

(Irradiation Step)

Hereinafter, the irradiation step in the image forming method isdescribed.

The irradiation step is not limited as long as the irradiation step is astep of irradiating the ink composition applied on the recording mediumwith the active energy rays.

If the ink composition is irradiated with active energy rays, thecrosslinking reaction of the gel particles in the ink compositionproceeds, the image is fixed, and the film hardness of the image isimproved.

Examples of the active energy rays that can be used in the irradiationstep include ultraviolet rays (UV light), visible rays, electron rays,and the like. Among these, ultraviolet rays (UV light) are preferable.

The peak wavelength of the active energy rays (light) depends onabsorbing characteristics of the sensitizing agent used, if necessary.For example, the peak wavelength is preferably 200 nm to 405 nm, morepreferably 220 nm to 390 nm, and even more preferably 220 nm to 385 nm.

In a case where the sensitizing agent is not used together, for example,the peak wavelength is preferably 200 nm to 310 nm and more preferably200 nm to 280 nm.

For example, the exposure surface illuminance at the time of irradiationwith the active energy rays (light) is preferably 10 mW/cm² to 2,000mW/cm² and irradiation is appropriately performed at 20 mW/cm² to 1,000mW/cm².

As the light source for generating the active energy rays (light), amercury lamp, a metal halide lamp, a UV fluorescent lamp, a gas laser, asolid-state laser, and the like are widely known.

The replacement of the light sources exemplified above into asemiconductor ultraviolet light emitting device is industrially andenvironmentally useful.

Among these, among semiconductor ultraviolet light emitting devices,light emitting diode (LED) (preferably, UV-LED) and a laser diode (LD)(preferably, UV-LD) are compact, has long lifetime, high efficiency, andlow cost, and is expected as a light source.

As the light source, a metal halide lamp, an extra high pressure mercurylamp, a high pressure mercury lamp, a medium pressure mercury lamp, alow pressure mercury lamp, LED, and a blue-violet laser are preferable.

Among these, in a case where the sensitizing agent is used together, anextra high pressure mercury lamp that can perform irradiation with lightat a wavelength of 365 nm, 405 nm, or 436 nm, a high pressure mercurylamp that can perform irradiation with light at a wavelength of 365 nm,405 nm, or 436 nm, LED that can perform irradiation with light at awavelength of 355 nm, 365 nm, 385 nm, and 395 nm, or 405 nm is morepreferable, and LED that can perform irradiation with light at awavelength of 355 nm, 365 nm, 385 nm, 395 nm, or 405 nm is mostpreferable.

Since the gel particles have functional groups that generate radicals byirradiation with active energy rays in the ink composition used in theimage forming method, a photopolymerization initiator that cannot beused in aqueous ink in the related art, for example, a structure whichis the same as a photopolymerization initiator such as an acylphosphineoxide compound having excellent sensitivity to light and low solubilityto water, can be selected.

For example, in a case where gel particles having a group including atleast one structure selected from a monoacylphosphine oxide structurethat has an absorption wavelength of 350 nm to 450 nm and is representedby Formula J, a bisacylphosphine oxide structure represented by FormulaK, and a bisacylphosphine oxide structure represented by Formula L and asensitizing agent such as a thioxanthone compound are used together, LEDis particularly preferable as the light source.

In a case where gel particles having a group including at least onestructure selected from a monoacylphosphine oxide structure representedby Formula J, a bisacylphosphine oxide structure represented by FormulaK, and a bisacylphosphine oxide structure represented by Formula L and asensitizing agent such as a thioxanthone compound are used together,active energy rays (light) that have a wavelength longer than that ofultraviolet rays and have a peak wavelength of 380 nm to 450 nm can bepreferably used.

In a case where gel particles having a group including at least onestructure selected from a monoacylphosphine oxide structure representedby Formula J, a bisacylphosphine oxide structure represented by FormulaK, and a bisacylphosphine oxide structure represented by Formula L and asensitizing agent are not used together, a metal halide lamp, a mediumpressure mercury lamp, and a low pressure mercury lamp are preferable asthe light source.

In the irradiation step, it is appropriate that the ink compositionapplied to the recording medium is irradiated with this UV light, forexample, for 0.01 seconds to 120 seconds, preferably 0.1 seconds to 90seconds.

With respect to the irradiation condition and the basic irradiationmethod, irradiation conditions and irradiation methods disclosed inJP1985-132767A (JP-S60-132767A) can be applied to the embodiment of theinvention, in the same manner. Specifically, a method of scanning thehead unit and the light sources by providing the light sources on bothsides of the head unit including the ink ejection device, by a so-calledshuttle method or a method of being performed by separate light sourcewithout driving is preferable. The irradiation of the active energy raysis performed for a certain period of time (for example, for 0.01 secondsto 120 seconds and preferably for 0.01 seconds to 60 seconds) after inklanding and drying by heating.

(Heating and Drying Step)

The image forming method may further have a heating and drying stepafter the ink applying step and before the irradiation step, ifnecessary.

In the heating and drying step, it is preferable that an image is fixedby evaporating water and a water-soluble organic solvent, which is usedtogether if necessary, by heating means from the ink composition ejectedon the recording medium.

A step (heating and drying step) of fixing the image by drying theejected ink composition by heating is described.

The heating means is not particularly limited, as long as the heatingmeans can dry water and the water-soluble organic solvent, which is usedtogether if necessary. However, a heat drum, hot air, an infrared lamp,a heat oven, and heat plate heating can be used.

The heating temperature is preferably 40° C. or higher, more preferablyabout 40° C. to 150° C., and even more preferably about 40° C. to 80° C.The drying and heating time can be appropriately set by adding thecomposition of the ink composition used and the printing speed.

The ink composition fixed by heating may be further optically fixed byirradiation with active energy rays in the irradiation step, ifnecessary. As described above, in the irradiation step, it is preferableto perform fixing by UV light.

EXAMPLES

Hereinafter, the embodiment of the invention is specifically describedwith reference to the specific examples, but the embodiment of theinvention is not limited to the examples below without departing fromthe gist of the invention.

[Synthesization of NCO103]

10 g of trimethylolpropane (TMP), 50.14 g of hexamethylene diisocyanate(HDI), and 111.69 g of ethyl acetate (AcOEt) were added to a three-neckflask and heated to 50° C., 0.172 g of TOYOCAT-RX21 (manufactured byTosoh Corporation, reactive catalyst) was added thereto, and reactionwas performed for six hours, so as to obtain NCO103.

[Synthesization of NCO109]

20 g of pentaerythritol ethylene oxide, 71.16 g of isophoronediisocyanate (IPDI), and 169.3 g of ethyl acetate (AcOEt) were added toa three-neck flask and heated to 50° C., 0.26 g of TOYOCAT-RX21(manufactured by Tosoh Corporation, reactive catalyst) was addedthereto, and reaction was performed for six hours, so as to obtainNCO109.

[Synthesization of INT-NCO1]

22.17 g of INT-1, 171.84 g of NCO103 (solid content: 35 mass %), and41.16 g of ethyl acetate (AcOEt) were added to a three-neck flask andheated to 50° C., 0.236 g of TOYOCAT-RX21 (manufactured by TosohCorporation, reactive catalyst) was added thereto, and reaction wasperformed for six hours, so as to obtain INT-NCO1 (a trifunctional orhigher isocyanate compound to which the functional group that generatedradicals due to active energy rays was introduced).

[Synthesization of INT-NCO9]

16.71 g of INT-5, 171.84 g of NCO103 (solid content: 35 mass %), and41.16 g of ethyl acetate (AcOEt) were added to a three-neck flask andheated to 50° C., 0.236 g of TOYOCAT-RX21 (manufactured by TosohCorporation, reactive catalyst) was added thereto, and reaction wasperformed for six hours, so as to obtain INT-NCO9 (a trifunctional orhigher isocyanate compound to which the functional group that generatedradicals due to active energy rays was introduced).

[Synthesization of INT-NCO11]

20 g of INT-5, 206.42 g of NCO109 (solid content: 35 mass %), and 37.13g of ethyl acetate were added to a three-neck flask and heated to 50°C., 0.318 g of TOYOCAT-RX21 (manufactured by Tosoh Corporation, reactivecatalyst) was added thereto, and reaction was performed for six hours,so as to obtain INT-NCO11 (a trifunctional or higher isocyanate compoundto which the functional group that generated radicals due to activeenergy rays was introduced).

[Synthesization of INT-NCO28]

10 g of trimethylolpropane (TMP), 66.27 g of isophorone diisocyanate(IPDI), and 185.2 g of ethyl acetate (AcOEt) were added to a three-neckflask and heated to 50° C., 0.285 g of TOYOCAT-RX21 (manufactured byTosoh Corporation, reactive catalyst) was added thereto, and reactionwas performed for three hours. After the reaction, 23.43 g of BLEMMERAP-400 (manufactured by NOF Corporation) was added thereto, and reactionwas further performed at 50° C. for six hours, so as to obtain INT-NCO28(a trifunctional or higher isocyanate compound to which a polymerizablegroup and a functional group that generated radicals due to activeenergy rays was introduced).

[Synthesization of Isocyanate Compound 1 to Which Hydrophilic Group wasIntroduced]

10 g of trimethylolpropane (TMP), 56.11 g of m-xylylene diisocyanate(XDI), and 132.2 g of ethyl acetate (AcOEt) were added to a three-neckflask and heated to 50° C., 0.04 g of TOYOCAT-RX21 (manufactured byTosoh Corporation, reactive catalyst) were added thereto, and reactionwas performed for three hours. 66.1 g of polyethylene glycol monomethylether (EO) (manufactured by Sigma-Aldrich Co. LLC., number-averagemolecular weight (Mn)=5,000) was added thereto, and reaction was furtherperformed for four hours, so as to obtain Isocyanate Compound 1 (anisocyanate compound including a group having a polyether structure,solid content: 50 mass %) to which a hydrophilic group was introduced.

[Synthesization of Isocyanate Compound 2 to Which Hydrophilic Group wasIntroduced]

45 g of 2,2-bis(hydroxymethyl) propionic acid (DMPA), 223.72 g ofisophorone diisocyanate (IPDI), and 499.05 g of ethyl acetate (AcOEt)were added to a three-neck flask and heated to 50° C., 0.7677 g ofTOYOCAT-RX21 (manufactured by Tosoh Corporation, reactive catalyst) wereadded thereto, and reaction was performed for three hours, so as toobtain Isocyanate Compound 2 (an isocyanate compound including acarboxylic acid group, solid content: 35 mass %) to which a hydrophilicgroup was introduced.

NCO104, NCO105, NCO112, and INT-NCO1 to INT-NCO27 represented by Tables3 and 4 below were produced in the same method as NCO103, NCO109,INT-NCO1, INT-NCO9, and INT-NCO11. The indication of the “initiator” inTable 4 represents an exemplary compound of a compound having at leastone active hydrogen group and at least one functional group thatgenerated radicals due to active energy rays, and the indication of the“isocyanate compound” represents a difunctional or higher isocyanatecompound.

TABLE 3 Composition Polyisocyanate structure Compound havingDifunctional Compound having two two or more isocyanate Compound or moreactive hydrogen active hydrogen groups compound Number groupsDifunctional isocyanate compound (mol equivalent) (mol equivalent) NCO103 NCO 104 NCO 105

  Trimethylolpropane Hexamethylene diisocyanate (HDI)1,3-bis(isocyanatomethyl) cyclohexane (HXDI) Isophorone diisocyanate(IPDI) 1 1 1 4 4 4 NCO 109

  Pentaerythritol ethylene oxide Isophorone diisocyanate (IPDI) 1 5 NCO112

  Triethanolamine Hexamethylene diisocyanate (HDI) 1 4

TABLE 4 Composition Amount of active hydrogen groups of initiator withrespect Addition method Compound to NCO group of Binding method toCompound Isocyanate isocyanate compound three-dimensional NumberInitiator compound (mol %) structure INT-NCO 1 INT-1 NCO 103 40 Sidechain type INT-NCO 2 INT-2 NCO 105 40 Main chain type INT-NCO 3 INT-3NCO 109 30 Main chain type INT-NCO 4 INT-4 TDI 37.5 Main chain typeINT-NCO 5 INT-4 HXDI 37.5 Main chain type INT-NCO 6 INT-4 HDI 37.5 Mainchain type INT-NCO 7 INT-4 IPDI 37.5 Main chain type INT-NCO 8 INT-4 XDI37.5 Main chain type INT-NCO 9 INT-5 NCO 103 40 Main chain type INT-NCO10 INT-5 NCO 104 40 Main chain type INT-NCO 11 INT-5 NCO 109 30 Mainchain type INT-NCO 12 INT-5 DURANATE 24A-100 40 Main chain type INT-NCO13 INT-5 TSE-100 40 Main chain type INT-NCO 14 INT-6 NCO 110 20 Mainchain type INT-NCO 15 INT-7 DURANATE TKA-100 40 Main chain type INT-NCO16 INT-8 NCO 103 40 Main chain type INT-NCO 17 INT-8 NCO 109 30 Mainchain type INT-NCO 18 INT-8 TSE-100 40 Main chain type INT-NCO 19 INT-9NCO 103 40 Side chain type INT-NCO 20 INT-10 IPDI 37.5 Side chain typeINT-NCO 21 INT-11 HDI 40 Side chain type INT-NCO 22 INT-11 HXDI 40 Sidechain type INT-NCO 23 INT-11 TMHDI 40 Side chain type INT-NCO 24 INT-12DURANATE TKA-100 40 Side chain type INT-NCO 25 INT-13 IPDI 37.5 Mainchain type INT-NCO 26 INT-14 NCO-112 40 Main chain type INT-NCO 27INT-15 HXDI 37.5 Main chain type

[Producing Dispersion Liquid of Gel Particles]

Example 1

<Emulsification Step>

—Producing of Oil Phase Component—

20 g of an isocyanate compound INT-NCO1 (solid content: 35 mass %) (antrifunctional or higher isocyanate compound to which the functionalgroup that generated radicals due to active energy rays was introduced),3.2 g of Isocyanate Compound 1 to which a hydrophilic group wasintroduced (solid content: 50 mass %), and 7 g of dipentaerythritolpentaacrylate (manufactured by Sartomer, SR-399E) (includedpolymerizable compound) were dissolved in 12 g of ethyl acetate, so asto obtain an oil phase component.

—Producing of Water Phase Component—

0.32 g of LAVELIN FP (surfactant) (manufactured by DKS Co., Ltd.) wasdissolved in 50 g of distilled water, so as to obtain a water phasecomponent.

The water phase component was added to the oil phase component, andmixed, and the obtained mixture was emulsified at 12,000 rpm for 10minutes by using a homogenizer, so as to obtain an emulsion.

<Gelation Step>

The obtained emulsion was added to 25 g of distilled water, stirred for30 minutes at room temperature, and stirred at 50° C. for three hours,and ethyl acetate was distilled.

Thereafter, stirring was performed at 50° C. for 24 hours, the obtaineddispersion liquid of the gel particles was diluted by using distilledwater such that the concentration of the solid content of the obtaineddispersion liquid became 20 mass %, so as to obtain dispersion liquid(water dispersion of gel particles) of Gel Particles 1. Thevolume-average particle diameter of the gel particles measured by thelight scattering method was 0.15 μm. In the measuring of thevolume-average particle diameter, a wet-type particle size distributionmeasuring device LA-910 (manufactured by Horiba Ltd.) was used.

[Preparation of Ink Composition]

Respective components were mixed by using the dispersion liquid of GelParticles 1 obtained as described above so as to become Ink Composition1 below, and an ink composition was prepared.

—Composition of Ink Composition 1—

Dispersion liquid of Gel Particles 1 82 parts Fluorine-based surfactant(manufactured by E. I. du 0.3 parts Pont de Nemours and Company,Capstone FS-31, solid content: 25 mass %) Ink (Pro-jet Cyan APD1000(manufactured by FUJIFILM 13 parts Imaging Colorants) colorantconcentration: 14 mass %) 2-methyl propane diol 4.7 parts

[Method of Evaluating Ink Composition]

A base material (vinyl chloride (PVC) sheet (manufactured by AveryDennison Corporation, AVERY 400 GLOSS WHITE PERMANENT)) was coated withthe produced ink composition in a thickness of 12 μm by using bar No. 2of K hand coater manufactured by RK PRINT COAT INSTRUMENTS Ltd. Afterthe coating, moisture was removed by drying the coated film at 60° C.for three minutes, so as to obtain a sample for evaluating the inkcomposition.

The obtained sample was evaluated as follows. Evaluation result arepresented in Table 6 below.

—Adhesiveness Evaluation A (Cross Hatch Test)—

The obtained sample for evaluating the ink composition was irradiatedwith active energy rays by a UV mini conveyor device for a test CSOT(manufactured by GS Yuasa International Ltd.) to which an ozonelessmetalhalide lamp MAN250L was mounted as an exposure light source and in whicha conveyor speed was set as 9.0 m/min and exposure intensity was set as2.0 W/cm², so as to to cure the sample. The adhesiveness to therecording medium was evaluated in standards as follows by using a curedcoated film in conformity with ISO2409 (cross cut method).

“%” representing peeling of a lattice in the standard of 0 to 5 as belowindicates a ratio of the number of lattices in which peeling wasobserved with respect to 25 of the number of lattices formed by beingcut at right angles at 1 mm intervals by percentage.Ratio of peeled lattice (%)=[(the number of lattice in which peeling wasgenerated)/(the total number of lattices)]×100

Evaluation standard

0: Cut edges were smooth, and peeling was not seen in all lattices.

1: Small peeling was observed in the coated film at intersection ofcuts. Portions at which the peeling was observed were 5% or less of thetotal number of lattices.

2: Peeling was observed in any one of portions along edges of cutportions of the coated film and intersections of cuts. The number ofportions in which peeling was observed was greater than 5% and 15% orless of the total number of lattices.

3: Peeling was partially or generally observed along edges of cutportions of the coated film or peeling was partially or generallyobserved in various portions of the lattice. The number of portions inwhich peeling was observed was greater than 15% and 35% or less of thetotal number of lattices.

4: Peeling was partially or generally observed along edges of cutportions of the coated film or peeling was partially or generallyobserved in various portions of the lattice. The number of portions inwhich peeling was observed was greater than 35% and 65% or less of thetotal number of lattices.

5: The number of portions in which peeling was observed was greater than65% of the total number of lattices.

In the evaluation, it is evaluated that 0 to 1 are levels that areacceptable in practice.

—Fixing Property Evaluation—

The obtained sample for evaluating the ink composition was exposed inthe condition of energy of 1,000 mJ/cm² by a Deep UV lamp (manufacturedby Ushio Inc., SP-7). A fixation degree on the surface of the sampleafter exposure was evaluated by touch. In a case where stickinessremains, exposure was repeated until the stickiness was removed, and thefixing properties were evaluated by an exposure amount until thestickiness was removed.

Evaluation standard

A: Stickiness was removed by exposure of one time.

B: Stickiness was removed by exposure of two to three times.

C: Stickiness was removed by exposure of four to five times.

D: Stickiness was not removed by exposure of six or more times.

—Solvent Resistance—

The obtained sample for evaluating the ink composition was exposed inthe condition of energy of 8,000 mJ/cm² by a Deep UV lamp (manufacturedby Ushio Inc., SP-7). The surface of a printed matter exposed in theenergy condition of 8,000 mJ/cm² was rubbed with a swab impregnated withisopropyl alcohol and visually evaluated according to the followingstandard.

Evaluation standard

A: Even if the surface was rubbed 10 or more times, no change in theimage was acknowledged.

B: Concentration of the image was decreased by rubbing of five times tonine times.

C: Concentration of the image was decreased by rubbing of two times tofour times.

D: Concentration of the image was remarkably decreased by rubbing of onetime.

—Water Resistance—

The obtained sample for evaluating the ink composition was exposed inthe condition of energy of 8,000 mJ/cm² by a Deep UV lamp (manufacturedby Ushio Inc., SP-7). The surface of a printed matter exposed in theenergy condition of 8,000 mJ/cm² was rubbed with a swab impregnated withwater and visually evaluated according to the following standard.

Evaluation Standard

A: Even if the surface was rubbed 10 or more times, no change in theimage was acknowledged.

B: Concentration of the image was decreased by rubbing of five times tonine times.

C: Concentration of the image was decreased by rubbing of two times tofour times.

D: Concentration of the image was remarkably decreased by rubbing of onetime.

—Redispersibility Evaluation—

An aluminum plate was coated with the ink composition in a thickness of12 μm by using bar No. 2 of K hand coater manufactured by RK PRINT COATINSTRUMENTS Ltd. After the coating, moisture was removed by drying thecoated film at 60° C. for three minutes. The surface of the coated filmwas rubbed with a sponge impregnated with water.

Fourier transform infrared spectroscopy (FT-IR) was performedrespectively on the coated film before being rubbed with a sponge andthe coated film after being rubbed, and the residual ratio of the gelparticles was calculated according to the equation below from obtainedresults.Residual ratio of gel particles=(Intensity of peak derived from gelparticles in coating film after being rubbed with sponge/Intensity ofpeak derived from gel particles in coating film before being rubbed withsponge)×100

Here, the peak derived from the gel particles is a peak of 1,700 cm⁻¹.

Redispersibility of the ink composition was evaluated in the evaluationstandards as below based on the residual ratio of the obtained gelparticles.

Evaluation Standard

A: A residual ratio of the gel particles was 1% or less.

B: A residual ratio of the gel particles was greater than 1% and 5% orless.

C: A residual ratio of the gel particles was greater than 5% and 10% orless.

D: A residual ratio of the gel particles was greater than 10%.

—Jettability Evaluation—

Ejection from the head was performed for 30 minutes by using an ink jetprinter (manufactured by Roland DG Corporation, SP-300V) and stopped.After five minutes have elapsed, ejection was performed again, so as torecord a solid image and a thin line on the recording medium(manufactured by Avery Dennison Corporation, AVERY 400 GLOSS WHITEPERMANENT). The obtained image (5 cm×5 cm) was observed, and evaluationwas visually performed by the evaluation standard below.

Evaluation Standard

A: Dot losses were not acknowledged, and an image with satisfactoryquality was able to be obtained.

B: Some dot losses were acknowledged, but no troubles were generated inqualities in practice.

C: Dot losses were generated, but troubles were generated in qualitiesin practice.

D: Ejection was not able to be performed.

—Preservation Stability Evaluation of Ink Composition—

The obtained ink composition was sealed in a container, two weeks hadelapsed at 60° C., evaluations such as the jettability evaluation wereperformed, and evaluations were performed in the same standards.

—Migration Property Evaluation—

A solid image (0.01 m² or greater) was formed on the recording medium(manufactured by Avery Dennison Corporation, AVERY 400 GLOSS WHITEPERMANENT) by using an ink jet printer (manufactured by Roland DGCorporation, SP-300V). A recording medium on which the solid image wasformed was cut into a size of 0.01 m², and 10 mL of mixture liquid ofwater:ethano1=70:30 was added dropwise on an image formed surface. Therecording medium after dropwise addition was put into a glass airtightcontainer such that the water-ethanol mixture liquid was not able to bevolatilized and was left alone at 40° C. for 10 days. After 10 days, atotal elution amount (overall migration limit: OML) of elutioncomponents eluted from the solid image contained in the water-ethanolmixture liquid was measured, and evaluation was performed according toevaluation standards below. The measurement of the total elution amountwas performed by volatilizing the water-ethanol mixture liquid after therecording medium was left alone for 10 days and measuring the mass ofthe residual components.

Evaluation Standard

A: The elution amount was 10 ppb or less.

B: The elution amount was greater than 10 ppb and 50 ppb or less.

C: The elution amount was greater than 50 ppb and 100 ppb or less.

D: The elution amount was greater than 100 ppb and 2,000 ppb or less.

E: The elution amount was greater than 2,000 ppb.

[Preparation of Photosensitive Composition]

Respective components were mixed so as to form photosensitivecomposition below by using a dispersion liquid of Gel Particles 1obtained described above and the photosensitive composition wasprepared.

—Composition of Photosensitive Composition—

Dispersion liquid of Gel Particles 1 81 parts Fluorine-based surfactant(manufactured by 0.3 parts E. I. du Pont de Nemours and Company,Capstone FS-31) Water The remainder with the whole as 100 parts

[Method of Evaluating Photosensitive Composition]

A base material (triacetylcellulose (TAC) film, manufactured by FujifilmCorporation) was coated with the produced photosensitive composition ina thickness of 12 μm by using bar No. 2 of K hand coater manufactured byRK PRINT COAT INSTRUMENTS Ltd. After the coating, moisture was removedby drying the coated film at 60° C. for three minutes, so as to obtain asample for evaluating a photosensitive composition.

The following evaluation was performed on the obtained sample forevaluating a photosensitive composition. Evaluation results arepresented in Table 6 below.

—Adhesiveness Evaluation B (Cross Hatch Test)—

The sample for evaluating the photosensitive composition was irradiatedwith active energy rays by a UV mini conveyor device for a test CSOT(manufactured by GS Yuasa International Ltd.) to which an ozonelessmetalhalide lamp MAN250L was mounted as an exposure light source and in whicha conveyor speed was set as 9.0 m/min and exposure intensity was set as2.0 W/cm², so as to to cure the sample. The adhesiveness to therecording medium was evaluated in standards as follows by using a curedcoated film in conformity with ISO2409 (cross cut method).

“%” representing peeling of a lattice in the standard of 0 to 5 as belowindicates a ratio of the number of lattices in which peeling wasobserved with respect to 25 of the number of lattices formed by beingcut at right angles at 1 mm intervals by percentage.Ratio of peeled lattice (%)=[(the number of lattice in which peeling wasgenerated)/(the total number of lattices)]×100

Evaluation Standard

0: Cut edges were smooth, and peeling was not seen in all lattices.

1: Small peeling was observed in the coated film at intersection ofcuts. Portions at which the peeling was observed were 5% or less of thetotal number of lattices.

2: Peeling was observed in any one of portions along edges of cutportions of the coated film and intersections of cuts. The number ofportions in which peeling was observed was greater than 5% and 15% orless of the total number of lattices.

3: Peeling was partially or generally observed along edges of cutportions of the coated film or peeling was partially or generallyobserved in various portions of the lattice. The number of portions inwhich peeling was observed was greater than 15% and 35% or less of thetotal number of lattices.

4: Peeling was partially or generally observed along edges of cutportions of the coated film or peeling was partially or generallyobserved in various portions of the lattice. The number of portions inwhich peeling was observed was greater than 35% and 65% or less of thetotal number of lattices.

5: The number of portions in which peeling was observed was greater than65% of the total number of lattices.

In the evaluation, it is evaluated that 0 to 1 are levels that areacceptable in practice.

—Pencil Hardness—

A pencil hardness test was performed on an ink cured film produced inthe same manner as in the adhesiveness evaluation, in conformity withJIS K5600-5-4 (1999). In the photosensitive composition, an allowablerange of the hardness is HB or harder and preferably H or harder. Aprinted matter having the evaluation result of B or less is notpreferable, since there is a possibility that scratches may be generatedat the time of handling the printed matter.

UNI (registered trademark) manufactured by Mitsubishi Pencil Co., Ltd.was used.

Examples 2 to 33 are represented below.

In Examples 2 to 33, gel particles were produced in the method describedbelow, the ink compositions and the photosensitive compositions wereprepared by using dispersion liquids of the gel particles produced inthe same manner as in Example 1, and various evaluations were performed.The evaluation results are provided in Table 6 below.

Examples 2 to 16

Dispersion liquids of Gel Particles 2 to 16 were produced in the samemanner as in Example 1 except for changing the trifunctional or higherisocyanate compound (INT-NCO1) used in Example 1 to trifunctional orhigher isocyanate compounds (INT-NCO) to which the functional groupsthat generated radicals due to active energy rays was introduced aspresented in Table 5 below.

Example 17

<Emulsification Step>

—Producing of Oil Phase Component—

15.46 g of isocyanate compound INT-NCO20 (solid content: 35 mass %) (atrifunctional or higher isocyanate compound to which the functionalgroup that generated radicals due to active energy rays was introduced),4.54 g of INT-NCO27 (solid content: 35 mass %) (a trifunctional orhigher isocyanate compound to which the functional group that generatedradicals due to active energy rays was introduced), 3.2 g of IsocyanateCompound 1 (solid content: 50 mass %) to which a hydrophilic group wasintroduced, and 7 g of dipentaerythritol pentaacrylate (manufactured bySartomer, SR-399E) (included polymerizable monomer) were dissolved in 12g of ethyl acetate, so as to obtain an oil phase component.

—Producing of Water Phase Component—

0.32 g of LAVELIN FP (surfactant) (manufactured by DKS Co., Ltd.) wasdissolved in 50 g of distilled water, so as to obtain a water phasecomponent.

The water phase component was added to the oil phase component, andmixed, and the obtained mixture was emulsified at 12,000 rpm for 10minutes by using a homogenizer, so as to obtain an emulsion.

<Gelation Step>

The obtained emulsion was added to 25 g of distilled water, stirred for30 minutes at room temperature, and stirred at 50° C. for three hours,and ethyl acetate was distilled.

Thereafter, stirring was performed at 50° C. for 24 hours, the obtaineddispersion liquid of the gel particles was diluted by using distilledwater such that the concentration of the solid content of the obtaineddispersion liquid became 20 mass %, so as to obtain a dispersion liquidof Gel Particles 17. The volume-average particle diameter of the gelparticles measured by the light scattering method was 0.15 μm.

Example 18

<Emulsification Step>

—Producing of Oil Phase Component—

22.34 g of isocyanate compound INT-NCO9 (solid content: 35 mass %) (atrifunctional or higher isocyanate compound to which the functionalgroup that generated radicals due to active energy rays was introduced),2.28 g of Isocyanate Compound 2 to which the hydrophilic group wasintroduced, and 7 g of dipentaerythritol pentaacrylate (manufactured bySartomer, SR-399E) (included polymerizable monomer) were dissolved in 12g of ethyl acetate, so as to obtain an oil phase component.

—Producing of Water Phase Component—

0.32 g of LAVELIN FP (surfactant) (manufactured by DKS Co., Ltd.) and0.035 g of sodium hydroxide were dissolved in 50 g of distilled water,so as to obtain a water phase component.

The water phase component was added to the oil phase component, andmixed, and the obtained mixture was emulsified at 12,000 rpm for 10minutes by using a homogenizer, so as to obtain an emulsion.

<Gelation Step>

The obtained emulsion was added to 25 g of distilled water, stirred for30 minutes at room temperature, and stirred at 50° C. for three hours,and ethyl acetate was distilled.

Thereafter, stirring was performed at 50° C. for 24 hours, the obtaineddispersion liquid of the gel particles was diluted by using distilledwater such that the concentration of the solid content of the obtaineddispersion liquid became 20 mass %, so as to obtain a dispersion liquidof Gel Particles 18. The volume-average particle diameter of the gelparticles measured by the light scattering method was 0.15 μm.

Examples 19 to 21

Dispersion liquids of Gel Particles 19 to 21 were produced in the samemanner as in Example 18 except for changing the trifunctional or higherisocyanate compound (INT-NCO9) used in Example 18 to trifunctional orhigher isocyanate compounds (INT-NCO) to which the functional group thatgenerated radicals due to active energy rays was introduced asrepresented in Table 5 below.

Example 22

<Emulsification Step>

—Producing of Oil Phase Component—

17.3 g of an isocyanate compound INT-NCO9 (solid content: 35 mass %) (atrifunctional or higher isocyanate compound to which the functionalgroup that generated radicals due to active energy rays was introduced),3.5 g of Isocyanate Compound 1 (solid content: 50 mass %) to which ahydrophilic group was introduced, 2.28 g of Isocyanate Compound 2 towhich a hydrophilic group was introduced, and 7 g of dipentaerythritolpentaacrylate (manufactured by Sartomer, SR-399E) (includedpolymerizable monomer) were dissolved in 12 g of ethyl acetate, so as toobtain an oil phase component.

—Producing of Water Phase Component—

0.4 g of LAVELIN FP (surfactant) (manufactured by DKS Co., Ltd.) and0.035 g of sodium hydroxide were dissolved in 50 g of distilled water,so as to obtain a water phase component.

The water phase component was added to the oil phase component, andmixed, and the obtained mixture was emulsified at 12,000 rpm for 10minutes by using a homogenizer, so as to obtain an emulsion.

<Gelation Step>

The obtained emulsion was added to 25 g of distilled water, stirred for30 minutes at room temperature, and stirred at 50° C. for three hours,and ethyl acetate was distilled.

Thereafter, stirring was performed at 50° C. for 24 hours, the obtaineddispersion liquid of the gel particles was diluted by using distilledwater such that the concentration of the solid content of the obtaineddispersion liquid became 20 mass %, so as to obtain a dispersion liquidof Gel Particles 22. The volume-average particle diameter of the gelparticles measured by the light scattering method was 0.15 μm.

Examples 23 to 25

Dispersion liquids of Gel Particles 23 to 25 were produced in the samemanner as in Example 22 except for changing the trifunctional or higherisocyanate compound (INT-NCO9) used in Example 22 to trifunctional orhigher isocyanate compounds (INT-NCO) to which the functional groupsthat generated radicals due to active energy rays was introduced aspresented in Table 5 below.

Example 26

<Emulsification Step>

—Producing of Oil Phase Component—

20 g of an isocyanate compound INT-NCO11 (solid content: 35 mass %) (atrifunctional or higher isocyanate compound to which the functionalgroup that generated radicals due to active energy rays was introduced),3.2 g of Isocyanate Compound 1 (solid content: 50 mass %) to which ahydrophilic group was introduced, and 7 g of neopentyl glycol propyleneoxide adduct diacrylate (manufactured by Sartomer, SR9003, NPGPODA)(included polymerizable monomer) were dissolved in 12 g of ethylacetate, so as to obtain an oil phase component.

—Producing of Water Phase Component—

0.32 g of LAVELIN FP (surfactant) (manufactured by DKS Co., Ltd.) wasdissolved in 50 g of distilled water, so as to obtain a water phasecomponent.

The water phase component was added to the oil phase component, andmixed, and the obtained mixture was emulsified at 12,000 rpm for 10minutes by using a homogenizer, so as to obtain an emulsion.

<Gelation Step>

The obtained emulsion was added to 25 g of distilled water, stirred for30 minutes at room temperature, and stirred at 50° C. for three hours,and ethyl acetate was distilled.

Thereafter, stirring was performed at 50° C. for 24 hours, the obtaineddispersion liquid of the gel particles was diluted by using distilledwater such that the concentration of the solid content of the obtaineddispersion liquid became 20 mass %, so as to obtain a dispersion liquidof Gel Particles 26. The volume-average particle diameter of the gelparticles measured by the light scattering method was 0.15 μm.

Examples 27 to 30

Dispersion liquids of Gel Particles 27 to 30 were produced in the samemanner as in Example 26 except for changing the included polymerizablemonomer (NPGPODA) used in Example 26 to included polymerizable monomerspresented in Table 5 below.

Example 31

<Emulsification Step>

—Producing of Oil Phase Component—

20 g of an isocyanate compound INT-NCO1 (solid content: 35 mass %) (atrifunctional or higher isocyanate compound to which the functionalgroup that generated radicals due to active energy rays was introduced),3.2 g of Isocyanate Compound 1 (solid content: 50 mass %) to which ahydrophilic group was introduced, and 20 g of INT-NCO28 (solid content:35 mass %) (a trifunctional or higher isocyanate compound to which apolymerizable group and a functional group that generated radicals dueto active energy rays was introduced) were dissolved in 2 g of ethylacetate, so as to obtain an oil phase component.

—Producing of Water Phase Component—

0.32 g of LAVELIN FP (surfactant) (manufactured by DKS Co., Ltd.) wasdissolved in 50 g of distilled water, so as to obtain a water phasecomponent.

The water phase component was added to the oil phase component, andmixed, and the obtained mixture was emulsified at 12,000 rpm for 10minutes by using a homogenizer, so as to obtain an emulsion.

<Gelation Step>

The obtained emulsion was added to 25 g of distilled water, stirred for30 minutes at room temperature, and stirred at 50° C. for three hours,and ethyl acetate was distilled.

Thereafter, stirring was performed at 50° C. for 24 hours, the obtaineddispersion liquid of the gel particles was diluted by using distilledwater such that the concentration of the solid content of the obtaineddispersion liquid became 20 mass %, so as to obtain a dispersion liquidof Gel Particles 31. The volume-average particle diameter of the gelparticles measured by the light scattering method was 0.15 μm.

Example 32

<Emulsification step>

—Producing of Oil Phase Component—

22.34 g of an isocyanate compound INT-NCO1 (solid content: 35 mass %) (atrifunctional or higher isocyanate compound to which the functionalgroup that generated radicals due to active energy rays was introduced),2.28 g of Isocyanate Compound 2 to which a hydrophilic group wasintroduced, and 20 g of INT-NCO28 (solid content: 35 mass %) (atrifunctional or higher isocyanate compound to which a polymerizablegroup and a functional group that generated radicals due to activeenergy rays was introduced) were dissolved in 2 g of ethyl acetate, soas to obtain an oil phase component.

—Producing of Water Phase Component—

0.32 g of LAVELIN FP (surfactant) (manufactured by DKS Co., Ltd.) and0.035 g of sodium hydroxide were dissolved in 50 g of distilled water,so as to obtain a water phase component.

The water phase component was added to the oil phase component, andmixed, and the obtained mixture was emulsified at 12,000 rpm for 10minutes by using a homogenizer, so as to obtain an emulsion.

<Gelation Step>

The obtained emulsion was added to 25 g of distilled water, stirred for30 minutes at room temperature, and stirred at 50° C. for three hours,and ethyl acetate was distilled.

Thereafter, stirring was performed at 50° C. for 24 hours, the obtaineddispersion liquid of the gel particles was diluted by using distilledwater such that the concentration of the solid content of the obtaineddispersion liquid became 20 mass %, so as to obtain a dispersion liquidof Gel Particles 32. The volume-average particle diameter of the gelparticles measured by the light scattering method was 0.15 μm.

Example 33

<Emulsification Step>

—Producing of Oil Phase Component—

17.3 g of the isocyanate compound MI-NCO9 (solid content: 35 mass %) (atrifunctional or higher isocyanate compound to which the functionalgroup that generated radicals due to active energy rays was introduced),3.5 g of Isocyanate Compound 1 (solid content: 50 mass %) to which ahydrophilic group was introduced, 4.56 g of Isocyanate Compound 2 towhich a hydrophilic group was introduced, and 7 g of dipentaerythritolpentaacrylate (manufactured by Sartomer, SR-399E) (includedpolymerizable monomer) were dissolved in 12 g of ethyl acetate, so as toobtain an oil phase component.

—Producing of Water Phase Component—

0.07 g of sodium hydroxide was dissolved in 50 g of distilled water, soas to obtain a water phase component.

The water phase component was added to the oil phase component, andmixed, and the obtained mixture was emulsified at 12,000 rpm for 10minutes by using a homogenizer, so as to obtain an emulsion.

<Gelation Step>

The obtained emulsion was added to 25 g of distilled water, stirred for30 minutes at room temperature, and stirred at 50° C. for three hours,and ethyl acetate was distilled.

Thereafter, stirring was performed at 50° C. for 24 hours, the obtaineddispersion liquid of the gel particles was diluted by using distilledwater such that the concentration of the solid content of the obtaineddispersion liquid became 20 mass %, so as to obtain a dispersion liquidof Gel Particles 33. The volume-average particle diameter of the gelparticles measured by the light scattering method was 0.15 μm.

<Checking Whether Dispersion Liquids of Gel Particles Includes GelParticles Having Polymerizable Groups>

Whether gel particles are actually included in the dispersion liquids ofthe gel particles of Examples 1 to 33 obtained described above ischecked by a method described below. The operation described below wasperformed in the condition of the liquid temperature of 25° C.

Samples were gathered from the dispersion liquids of the gel particlesdescribed below. 100 times by mass of tetrahydrofuran (THF) with respectto a total solid content (particles in this example) in this sample wasadded to and mixed with the gathered samples, so as to prepare diluentsof the dispersion liquids of the gel particles. Centrifugation (80,000rpm, for 40 minutes) was performed on the obtained diluents. After thecentrifugation, whether residues exist was visually checked. In a casewhere the residues were checked, redispersion of the residues in waterwas performed by adding water to this residue and performing stirringfor one hour by using a stirrer so as to obtain a redispersion liquid.Particle size distribution of the obtained redispersion liquid wasmeasured by the light scattering method, by using a wet-type particlesize distribution measuring device (LA-910, manufactured by HoribaLtd.). In a case where particle size distribution was checked by theoperation above, it was determined that the dispersion liquid includegel particles.

As a result, it was checked that the dispersion liquids of all of thegel particles include gel particles.

From the results above and results of the fourier transform infraredspectroscopy (FT-IR) analysis, it was checked that all of the dispersionliquids of the gel particles included gel particles having polymerizablegroups (that is, the gel particles were the gel particles actuallyhaving polymerizable groups).

<Checking of Inclusion of Polymerizable Monomer>

With respect to the dispersion liquids of the gel particles using thepolymerizable monomer in the production among the dispersion liquids ofthe gel particles of Examples 1 to 33 obtained above, an inclusion ratio(%) of the polymerizable monomer was measured so as to check whether thepolymerizable monomers are included in the gel particles. Detailsthereof are described below. Operations below are performed in thecondition of the liquid temperature of 25° C.

Two samples in the same mass (hereinafter, referred to as “Sample 1A”and “Sample 2A”) were gathered from the dispersion liquids of the gelparticles.

100 times by mass of tetrahydrofuran (THF) of the total solid content inSample 1A was added to and mixed with Sample 1A, so as to preparediluents. Centrifugation was performed on the obtained diluents in thecondition of 80,000 rpm and 40 minutes. The supernatant (hereinafter,referred to as “Supernatant 1A”) generated by the centrifugation wasgathered. The mass of the polymerizable monomer included in Supernatant1A gathered was measured by “Waters2695” a liquid chromatography devicemanufactured by Waters Corporation. The mass of the obtainedpolymerizable monomer was set as “the total amount of the polymerizablemonomer”.

Centrifugation was performed on Sample 2A in the same condition as inthe centrifugation performed on the diluent. A supernatant (hereinafter,referred to as “Supernatant 2A”) generated by the centrifugation wasgathered. The mass of the polymerizable monomer included in Supernatant2A gathered was measured by the liquid chromatography device. The massof the obtained polymerizable monomer was “a liberation amount of thepolymerizable monomer”.

An inclusion ratio (mass %) of the polymerizable monomer was obtained byan equation below based on the “total amount of the polymerizablemonomer” and the “liberation amount of the polymerizable monomer”.Inclusion ratio (mass %) of polymerizable monomer=((Total amount ofpolymerizable monomer-liberation amount of polymerizable monomer)/totalamount of polymerizable monomer)×100

As a result, it was checked that a polymerizable monomer having aninclusion ratio of 99% or greater was included in the gel particles ofall the dispersion liquid of the gel particles used in the producedpolymerizable monomer.

Comparative Example 1

As the oil phase component, 20 g of NCO103 (solid content: 35 mass %)(trifunctional or higher isocyanate compound), 3.2 g of an adduct oftrimethylolpropane, xylene diisocyanate, and polyethylene glycolmonomethyl ether (manufactured by Mitsui Chemicals, Inc., TAKENATE(registered trademark) D-116N, a 50 mass % solution of ethyl acetate,isocyanate compound 3 to which a hydrophilic group was introduced), 7 gof dipentaerythritol pentaacrylate (manufactured by Sartomer, SR-399E)(included polymerizable monomer), and 1 g of Irgacure (registeredtrademark) 819 (manufactured by BASF SE) (included photopolymerizationinitiator) were dissolved in 12 g of ethyl acetate.

0.32 g of LAVELIN FP (surfactant) (manufactured by DKS Co., Ltd.) wasdissolved in 50 g of distilled water, so as to obtain a water phasecomponent.

The water phase component was added to the oil phase component, andmixed, and the obtained mixture was emulsified at 12,000 rpm for 10minutes by using a homogenizer, so as to obtain an emulsion.

After the obtained emulsion was added to 25 g of distilled water andstirred for 30 minutes at room temperature, stirring was furtherperformed at 50° C. for three hours, and ethyl acetate was distilled.

Thereafter, stirring was performed at 50° C. for 24 hours, the obtaineddispersion liquid of the gel particles was diluted by using distilledwater such that the concentration of the solid content of the obtaineddispersion liquid became 20 mass %, so as to obtain a dispersion liquidof Comparative Particles 1. The volume-average particle diameter of thegel particles measured by the light scattering method was 0.15 μm. Inthe measurement of the volume-average particle diameter, a wet-typeparticle size distribution measuring device LA-910 (manufactured byHoriba Ltd.) was used.

In the dispersion liquid of Comparative Particles 1, ComparativeParticles 1 did not have the functional group that generated radicals byirradiation with active energy rays.

Comparative Examples 2 to 5

Dispersion liquids of Comparative Particles 2 to 5 were produced in thesame manner as Comparative Example 1 except for changing the includedphotopolymerization initiator (Irgacure (registered trademark) 819) usedin Comparative Example 1 to included photopolymerization initiatorsrepresented in Table 5 below.

In the dispersion liquids of Comparative Particles 2 to 5, all ofComparative Particles 2 to 5 did not have the functional groups thatgenerate radicals by irradiation with active energy rays.

TABLE 5 Gel Particle Isocyanate compound to which Included Isocyanatecompound polymerizable photopoly- Included Gel Particle to whichhydrophilic group was merization polymerizable Number group wasintroduced introduced INT-NCO initiator monomer Surfactant Example 1 GelCompound 1 — — — INT-NCO 1  — SR-399E LAVELIN FP Particles 1 Example 2Gel Compound 1 — — — INT-NCO 3  — SR-399E LAVELIN FP Particles 2 Example3 Gel Compound 1 — — — INT-NCO 4  — SR-399E LAVELIN FP Particles 3Example 4 Gel Compound 1 — — — INT-NCO 5  — SR-399E LAVELIN FP Particles4 Example 5 Gel Compound 1 — — — INT-NCO 8  — SR-399E LAVELIN FPParticles 5 Example 6 Gel Compound 1 — — — INT-NCO 9  — SR-399E LAVELINFP Particles 6 Example 7 Gel Compound 1 — — — INT-NCO 11 — SR-399ELAVELIN FP Particles 7 Example 8 Gel Compound 1 — — — INT-NCO 12 —SR-399E LAVELIN FP Particles 8 Example 9 Gel Compound 1 — — — INT-NCO 13— SR-399E LAVELIN FP Particles 9 Example 10 Gel Compound 1 — — — INT-NCO16 — SR-399E LAVELIN FP Particles 10 Example 11 Gel Compound 1 — — —INT-NCO 20 — SR-399E LAVELIN FP Particles 11 Example 12 Gel Compound 1 —— — INT-NCO 22 — SR-399E LAVELIN FP Particles 12 Example 13 Gel Compound1 — — — INT-NCO 23 — SR-399E LAVELIN FP Particles 13 Example 14 GelCompound 1 — — — INT-NCO 24 — SR-399E LAVELIN FP Particles 14 Example 15Gel Compound 1 — — — INT-NCO 25 — SR-399E LAVELIN FP Particles 15Example 16 Gel Compound 1 — — — INT-NCO 26 — SR-399E LAVELIN FPParticles 16 Example 17 Gel Compound 1 — — — INT-NCO 20 — SR-399ELAVELIN FP Particles 17 INT-NCO 27 Example 18 Gel — Compound 2 — —INT-NCO 9  — SR-399E LAVELIN FP Particles 18 Example 19 Gel — Compound 2— — INT-NCO 11 — SR-399E LAVELIN FP Particles 19 Example 20 Gel —Compound 2 — — INT-NCO 12 — SR-399E LAVELIN FP Particles 20 Example 21Gel — Compound 2 — — INT-NCO 13 — SR-399E LAVELIN FP Particles 21Example 22 Gel Compound 1 Compound 2 — — INT-NCO 9  — SR-399E LAVELIN FPParticles 22 Example 23 Gel Compound 1 Compound 2 — — INT-NCO 11 —SR-399E LAVELIN FP Particles 23 Example 24 Gel Compound 1 Compound 2 — —INT-NCO 12 — SR-399E LAVELIN FP Particles 24 Example 25 Gel Compound 1Compound 2 — — INT-NCO 13 — SR-399E LAVELIN FP Particles 25 Example 26Gel Compound 1 — — — INT-NCO 11 — NPGPODA LAVELIN FP Particles 26Example 27 Gel Compound 1 — — — INT-NCO 11 — A-TMPT LAVELIN FP Particles27 Example 28 Gel Compound 1 — — — INT-NCO 11 — ATMM-3L LAVELIN FPParticles 28 Example 29 Gel Compound 1 — — — INT-NCO 11 — AD-TMP LAVELINFP Particles 29 Example 30 Gel Compound 1 — — — INT-NCO 11 — A-DPHLAVELIN FP Particles 30 Example 31 Gel Compound 1 — — INT-NCO 28 INT-NCO1  — — LAVELIN FP Particles 31 Example 32 Gel — Compound 2 — INT-NCO 28INT-NCO 1  — — LAVELIN FP Particles 32 Example 33 Gel Compound 1Compound 2 — — INT-NCO 9  — SR-399E — Particles 33 Comparative — — —Compound 3 — NCO 103 Irgacure 819 SR-399E LAVELIN FP Example 1Comparative — — — Compound 3 — NCO 103 Irgacure 369 SR-399E LAVELIN FPExample 2 Comparative — — — Compound 3 — NCO 103 Irgacure 2959 SR-399ELAVELIN FP Example 3 Comparative — — — Compound 3 — NCO 103 Photopoly-SR-399E LAVELIN FP Example 4 merization initiator 1 Comparative — — —Compound 3 — NCO 103 Photopoly- SR-399E LAVELIN FP Example 5 merizationinitiator 2

Compounds 1 to 3, INT-NCO28, and photopolymerization initiators 1 and 2in Table 5 were compounds in the structures presented below. Thephotopolymerization initiator 1 and the photopolymerization initiator 2were compounds disclosed in paragraph numbers [0305] to [0308] disclosedin JP2012-532238A. A-TMPT represents trimethylolpropane triacrylate,ATMM-3L represents pentaerythritol triacrylate, AD-TMP representsditrimethylolpropane tetraacrylate, and AD-DPH representsdipentaerythritol hexaacrylate (all are manufactured by Shin NakamuraChemical Co., Ltd.).

TABLE 6 Evaluation results Adhesiveness Pencil Water Solvent FixingPreservation Migration A B hardness resistance resistance propertiesJettability Redispersibility stability properties Example 1 0 0  F A A AA A A B Example 2 0 0 3H A A A A A A A Example 3 0 0 3H A A A A A A AExample 4 0 0 2H A A A A A A A Example 5 0 0 2H A A A A A A A Example 60 0  H A A A A A A A Example 7 0 0 3H A A A A A A A Example 8 0 0  H A AA A A A A Example 9 0 0  H A A A A A A A Example 10 0 0  H A A A A A A BExample 11 0 0 3H A A A A A A B Example 12 0 0 2H A A A A A A B Example13 0 0  H A A A A A A B Example 14 0 0  H A A A A A A B Example 15 0 02H A A B A A A A Example 16 0 0  F A A B A A A A Example 17 0 0 3H A A AA A A B Example 18 0 0  H A A A A A A A Example 19 0 0 3H A A A A A A AExample 20 0 0  H A A A A A A A Example 21 0 0  H A A A A A A A Example22 0 0  H A A A A A A A Example 23 0 0 3H A A A A A A A Example 24 0 0 H A A A A A A A Example 25 0 0  H A A A A A A A Example 26 0 0  H A A AA A A A Example 27 0 0 3H A A A A A A A Example 28 0 0 3H A A A A A A AExample 29 0 0 3H A A A A A A A Example 30 0 0 3H A A A A A A A Example31 0 0  F A A A A A A B Example 32 0 0  F A A A A A A B Example 33 0 0 H A A A A A A A Comparative 0 0  H A A A A A A C Example 1 Comparative0 0  H A A A A A A D Example 2 Comparative 0 0  H A A A A A A D Example3 Comparative 0 0  H A A B A A A C Example 4 Comparative 0 0  H A A B AA A C Example 5

In the ink compositions of the examples in Table 6, all of theadhesiveness, the water resistance, the solvent resistance, the fixingproperties, the jettability, the redispersibility, the preservationstability, and migration properties were excellent. In thephotosensitive compositions of the examples, the adhesiveness and thepencil hardness were excellent.

From these, it is understood that a film in which occurrence of themigration was suppressed and film hardness was excellent was able to beobtained in the examples.

Example 34 to Example 35

[Evaluation of ink composition using LED] The ink compositions ofExamples 11 and 17 using LED were evaluated.

Specifically, the same operations were performed as those inAdhesiveness Evaluation A, Adhesiveness Evaluation B, and PencilHardness Evaluation, except for changing the exposure light source(ozoneless metal halide lamp MAN250L) to a 385 nm UV-LED irradiator(manufactured by CCS Inc.) for a test and changing the exposure energiesto 300 mJ/cm².

Results there are provided in Table 7.

TABLE 7 Evaluation results Pencil Adhesiveness hardness PVC TAC Example34 Gel Particles 11  H 0 0 Example 35 Gel Particles 17 2H 0 0

As presented in Table 7, at the time of curing, the ink compositions ofExamples 11 and 17 using LED light exhibited excellent results of theadhesiveness and the pencil hardness evaluation in the same manner as ina case where the ozoneless metal halide lamp MAN250L was used (see Table6 above).

Example 36

[Preparation of ink composition] A cyan ink composition was prepared byusing the dispersion liquid of the gel particles of Example 4 and mixingrespective components so as to obtain a cyan ink composition asdescribed below.

—Composition of Cyan Ink Composition—

Dispersion liquid of Gel particles 4 75 parts SR9035 (manufactured bySartomer, ethoxylated 10 parts trimethylolpropane triacrylate,polymerizable compound) Ink (Pro-jet Cyan APD1000 (manufactured byFUJIFILM 10 parts Imaging Colorants, Inc.) colorant concentration: 14mass %) Fluorine-based surfactant (manufactured by E. I. du Pont de 0.3parts Nemours and Company, Capstone FS-31, solid content: 25 mass %)2-methyl propane diol 4.7 parts

Examples 37 to 40

Cyan ink compositions of respective examples were produced in the samemanner as in Example 36 except for changing SR9035 (polymerizablecompound) used as the cyan ink composition of Example 36 to apolymerizable compound presented in Table 8 below.

Examples 41 to 45

Cyan ink compositions of respective examples were produced in the samemanner as in Examples 36 to 40 except for changing Gel Particles 4 usedas the cyan ink compositions of Examples 36 to 40 to Gel Particles 23.

[Method of Evaluating Ink Composition]

Base materials (vinyl chloride sheets (manufactured by Avery DennisonCorporation, AVERY 400 GLOSS WHITE PERMANENT)) were coated withrespective cyan ink compositions of Examples 36 to 45 obtained above byusing bar No. 2 of K hand coater manufactured by RK PRINT COATINSTRUMENTS Ltd. such that a thickness became 12 μm. After the coating,moisture was dried from the coated film at 60° C. for three minutes, soas to obtain samples for evaluating the ink compositions.

With respect to the obtained samples, Adhesiveness Evaluation A, fixingproperty evaluation, solvent resistance evaluation, water resistanceevaluation, and pencil hardness evaluation were performed in the samemanner as described above. Evaluation results are provided in Table 9below.

With respect to the cyan ink compositions of Examples 36 to 45 obtainedabove, redispersibility evaluation and preservation stability evaluationwere performed in the same manner as in the method described above, andjettability evaluation was performed in a method described below.Evaluation results are provided in Table 9 below.

—Jettability Evaluation—

The cyan ink compositions of Examples 36 to 45 obtained above wereejected from the head for 30 minutes by using the ink jet printer(manufactured by Roland DG Corporation, SP-300V) and stopped. After fiveminutes had elapsed, the cyan ink compositions were ejected again torecording mediums (manufactured by Avery Dennison Corporation, AVERY 400GLOSS WHITE PERMANENT), so as to record solid images and thin lines. Theobtained images (5 cm×5 cm) were observed and were evaluated accordingto the evaluation standards below.

Evaluation Standard

A: Dot losses were not acknowledged, and an image with satisfactoryquality was able to be obtained.

B: Some dot losses were acknowledged, but no troubles were generated inqualities in practice.

C: Dot losses were generated, but troubles were generated in qualitiesin practice.

D: Ejection was not able to be performed.

TABLE 8 Polymerizable Gel Particles Compound Example 36 Ink Composition36 Gel Particles 4 SR9035 Example 37 Ink Composition 37 Gel Particles 4AM-1 Example 38 Ink Composition 38 Gel Particles 4 AM-2 Example 39 InkComposition 39 Gel Particles 4 AM-3 Example 40 Ink Composition 40 GelParticles 4 AM-4 Example 41 Ink Composition 41 Gel Particles 23 SR9035Example 42 Ink Composition 42 Gel Particles 23 AM-1 Example 43 InkComposition 43 Gel Particles 23 AM-2 Example 44 Ink Composition 44 GelParticles 23 AM-3 Example 45 Ink Composition 45 Gel Particles 23 AM-4

SR9035 in Table 8 was ethoxylated trimethylolpropane triacrylate(manufactured by Sartomer) and AM-1 to AM-4 were compounds in thestructures provided below.

TABLE 9 Evaluation results Adhesiveness Pencil Water Solvent FixingPreservation Migration Ink Composition A hardness resistance resistanceproperties Jettability Redispersibility stability properties Example 36Ink 0 2H A A A A A A A Composition 36 Example 37 Ink 0 2H A A A A A A AComposition 37 Example 38 Ink 0 2H A A A A A A A Composition 38 Example39 Ink 0 2H A A A A A A A Composition 39 Example 40 Ink 0 2H A A A A A AA Composition 40 Example 41 Ink 0 3H A A A A A A A Composition 41Example 42 Ink 0 3H A A A A A A A Composition 42 Example 43 Ink 0 3H A AA A A A A Composition 43 Example 44 Ink 0 3H A A A A A A A Composition44 Example 45 Ink 0 3H A A A A A A A Composition 45

It was understood that, in the ink compositions of Examples 36 to 45 aspresented in Table 9, all of the adhesiveness, the water resistance, thesolvent resistance, the fixing properties, the jettability, theredispersibility, and the preservation stability were excellent. Fromthis, it was understood that the examples had dispersibility andredispersibility, and it was possible to obtain an image havingexcellent film hardness by performing curing with high sensitivity.

The whole of the disclosure of JP2014-201982 filed on Sep. 30, 2014 andJP2015-061720 filed on Mar. 24, 2015 is incorporated into the presentspecification by reference.

All the documents, patent applications, and technical standardsdescribed in the specification are incorporated into the presentspecification by reference to the same extent as that in the case whereit is specifically and individually shown that each of the documents,patent applications, and technical standards is incorporated into thepresent specification by reference.

What is claimed is:
 1. Gel particles each having a three-dimensionalcrosslinked structure including at least one bond selected from aurethane bond and a urea bond, the gel particles each comprising: apolymerizable group; and a functional group that generates radicals byirradiation with active energy rays; wherein the polymerizable group isan ethylenically unsaturated group; and the functional group thatgenerates radicals by irradiation with active energy rays is bonded tothe three-dimensional crosslinked structure of the gel particles via acovalent bond.
 2. The gel particles according to claim 1, wherein thefunctional group that generates radicals by irradiation with activeenergy rays is a group having at least one selected from an acetophenonestructure represented by Formula A below, a monoacylphosphine oxidestructure represented by Formula B below, and a bisacylphosphine oxidestructure represented by Formula C below,

in Formulae A, B, and C, R's each independently represent a monovalentgroup or *-L-, at least one of R's in the respective formulae represents*-L-, L represents a divalent organic group, and * represents a bondingsite with a three-dimensional crosslinked structure.
 3. The gelparticles according to claim 1, each further comprising: a hydrophilicgroup on a surface.
 4. The gel particles according to claim 1, having avolume average particle diameter of 0.01 μm to 10.0 μm.
 5. The gelparticles according to claim 1, each further comprising: a polymerizablemonomer inside the gel particles.
 6. The gel particles according toclaim 5, wherein the polymerizable monomer includes a polymerizablemonomer having an ethylenically unsaturated group.
 7. The gel particlesaccording to claim 6, wherein the number of the ethylenicallyunsaturated group is three or more.
 8. A photosensitive compositioncomprising: the gel particles according to claim 1; and water.
 9. Thephotosensitive composition according to claim 8, further comprising: apolymerizable compound outside the gel particles.
 10. An ink compositioncomprising: the gel particles according to claim 1; water; and acolorant.
 11. The ink composition according to claim 10, furthercomprising: a polymerizable compound outside the gel particles.
 12. Animage forming method comprising: applying the ink composition accordingto claim 10 on a recording medium; and irradiating the ink compositionapplied on the recording medium with active energy rays.